Reuse the implementation for bytes since it works the same way regardless
of the underlying type.  This method gets added for CPython compatibility
of bytearray, but to keep the code simple and small array.array now also
has a working decode method, which is non-standard but doesn't hurt.

This allows figuring out the number of bytes in the memoryview object as
len(memview) * memview.itemsize.

The feature is enabled via MICROPY_PY_BUILTINS_MEMORYVIEW_ITEMSIZE and is
disabled by default.

Follow up to commit 34942d0a

Fixes issue #4780.

Fixes issue #4527.

Selectable at compile time via MICROPY_PY_UCRYPTOLIB_CTR.  Disabled by
default.

Variables with type bool now act more like an int, and there is proper
casting to/from Python objects.

Now that setblocking() is implemented in modussl_axtls, it calls into the
underlying stream object, and io.BytesIO doesn't have setblocking().

It consists of:

1. "do_handhake" param (default True) to wrap_socket(). If it's False,
handshake won't be performed by wrap_socket(), as it would be done in
blocking way normally. Instead, SSL socket can be set to non-blocking mode,
and handshake would be performed before the first read/write request (by
just returning EAGAIN to these requests, while instead reading/writing/
processing handshake over the connection). Unfortunately, axTLS doesn't
really support non-blocking handshake correctly. So, while framework for
this is implemented on MicroPython's module side, in case of axTLS, it
won't work reliably.

2. Implementation of .setblocking() method. It must be called on SSL socket
for blocking vs non-blocking operation to be handled correctly (for
example, it's not enough to wrap non-blocking socket with wrap_socket()
call - resulting SSL socket won't be itself non-blocking).  Note that
.setblocking() propagates call to the underlying socket object, as
expected.

This adds tests for some locations in the code where a memory allocation
should raise an exception.

When running Linux on WSL, Popen.kill() can raise a ProcessLookupError if
the process does not exist anymore, which can happen here since the
previous statement already tries to close the process by sending Ctrl-D to
the running repl.  This doesn't seem to be a problem on other OSes, so just
swallow the exception silently since it indicates the process has been
closed already, which after all is what we want.

This means the schedule operates on a first-in, first-executed manner
rather than the current last-in, first executed.

This is an implementation of a sliding qstr window used to reduce the
number of qstrs stored in a .mpy file.  The window size is configured to 32
entries which takes a fixed 64 bytes (16-bits each) on the C stack when
loading/saving a .mpy file.  It allows to remember the most recent 32 qstrs
so they don't need to be stored again in the .mpy file.  The qstr window
uses a simple least-recently-used mechanism to discard the least recently
used qstr when the window overflows (similar to dictionary compression).
This scheme only needs a single pass to save/load the .mpy file.

Reduces mpy file size by about 25% with a window size of 32.

POP_BLOCK and POP_EXCEPT are now the same, and are always followed by a
JUMP.  So this optimisation reduces code size, and RAM usage of bytecode by
two bytes for each try-except handler.

This patch fixes a bug in the VM when breaking within a try-finally.  The
bug has to do with executing a break within the finally block of a
try-finally statement.  For example:

    def f():
        for x in (1,):
            print('a', x)
            try:
                raise Exception
            finally:
                print(1)
                break
            print('b', x)
    f()

Currently in uPy the above code will print:

    a 1
    1
    1
    segmentation fault (core dumped)  micropython

Not only is there a seg fault, but the "1" in the finally block is printed
twice.  This is because when the VM executes a finally block it doesn't
really know if that block was executed due to a fall-through of the try (no
exception raised), or because an exception is active.  In particular, for
nested finallys the VM has no idea which of the nested ones have active
exceptions and which are just fall-throughs.  So when a break (or continue)
is executed it tries to unwind all of the finallys, when in fact only some
may be active.

It's questionable whether break (or return or continue) should be allowed
within a finally block, because they implicitly swallow any active
exception, but nevertheless it's allowed by CPython (although almost never
used in the standard library).  And uPy should at least not crash in such a
case.

The solution here relies on the fact that exception and finally handlers
always appear in the bytecode after the try body.

Note: there was a similar bug with a return in a finally block, but that
was previously fixed in b7352084

All exceptions that unwind through the async-with must be caught and
BaseException is the top-level class, which includes Exception and others.

Fixes issue #4552.

As mentioned in #4450, `websocket` was experimental with a single intended
user, `webrepl`. Therefore, we'll make this change without a weak
link `websocket` -> `uwebsocket`.

Configurable via MICROPY_PY_BUILTINS_NEXT2, disabled by default.

Instead of assuming that the method is a bytecode object, and only
supporting load of __name__, make the operation generic by delegating the
load to the method object itself.  Saves a bit of code size and fixes the
case of attempting to load __name__ on a native method, see issue #4028.

As per the machine.UART documentation, this is used to set the length of
the RX buffer.  The legacy read_buf_len argument is retained for backwards
compatibility, with rxbuf overriding it if provided.

Also change the order of printing of flow so it is after stop (so bits,
parity, stop are one after the other), and reduce code size by using
mp_print_str instead of mp_printf where possible.

See issue #1981.

After Unix port switches from one to another, to be consistent with
baremetal ports.

Such names aren't stored as qstr in module dict, and there was a bug in
"import *" handling which assumed any name in a module dict is a qstr.

CPython does not have an implementation of select.poll() on some
operating systems (Windows, OSX depending on version) so skip the
test in those cases instead of failing it.

This ensures that implicit variables are only converted to implicit
closed-over variables (nonlocals) at the very end of the function scope.
If variables are closed-over when first used (read from, as was done prior
to this commit) then this can be incorrect because the variable may be
assigned to later on in the function which means they are just a plain
local, not closed over.

Fixes issue #4272.

The way it was written previously the variable x was not an implicit
nonlocal, it was just a normal local (but the compiler has a bug which
incorrectly makes it a nonlocal).