change(uart): Use low power HIRC8 for uart clock

See merge request !477

Disable core 1 interrupts during API calls

See merge request !474

Disable all maskable interrupts on core 1 during API calls.  This brings
two main advantages:

1. It means API calls are now always ISR-safe and can be used everywhere
   in core 1 code.  This is mostly interesting to l0dables as Pycardium
   should not need to do this.

2. It allows Epicardium to halt the clock for core 1 without fear as we
   have observed problems with doing this when core 1 is currently
   executing instructions that touch memory.  Now a synchronous call
   from core 1 will guarantee that it is currently waiting in a WFE and
   no other ISRs could be potentially running.

When interrupts are disabled during API calls on core 1, we can only
trigger a core 1 reset when there is no API call ongoing.  This means
that the lifecycle machinery needs to allow any running API calls to
complete before it has a chance to see its reset interrupt delivered.

This is complicated because we cannot synchronize on core 1 triggering
an API call - the best we can do is stop the dispatcher, check whether
our reset interrupt was delivered, and if not, give it another chance to
process an API call.

Additionally, "give it another chance to process an API call" means that
the IDLE task must run, because this is currently a prerequisite to
scheduling the dispatcher (see [1]).  The only way to facilitate this is
with a sleep that is long enough that it will eventually let core 0 go
idle.  It seems that an 8 tick delay does the job quite fine.

Thus, implement a busy loop which provides the above requirements and
with that makes Epicardium prepared for payloads which perform API calls
with interrupts disabled.

[1]: https://firmware.card10.badge.events.ccc.de/epicardium/overview.html#internals

This function is useful on its own for more complex lifecycle management
in Epicardium.  Split it out of core1_wait_ready() so it can be used.

Cleanup epicardium structure

See merge request !472

As a part of this, drop os/log.h.  Also add documentation for this.

See merge request !470

Automatically exit the "USB storage mode" once the connected USB host
ejects card10.

Add an `os.fs_is_attached()` function to allow apps to check whether the
filesystem is available.

Release 1.17 - R2R Rocket

See merge request !469

Update CHANGELOG

See merge request !467

feat(epicardium): Add v1.17 splash

See merge request !463

Make sleep work again when BLE is disabled

Closes #231

See merge request !466

In commit 4944aa48 ("fix(ble): Update to changes from new SDK")
a call to `BbDrvDisable()` was added to `sleep_deepsleep()`.  This
function must, however, only be called when BLE was previously
initialized, otherwise a wakeup from deepsleep will not be possible (if
it ever reaches it?).

Fix this by reworking the BLE enabled check to also be usable here, to
only call `BbDrvDisable()` when BLE is active.

Fixes: 4944aa48 ("fix(ble): Update to changes from new SDK")
Fixes: #231

Add config option to disable low battery check

Closes #227

See merge request !464

We have encountered a device where the connection from the PMIC's ADMUX
pin to the MCUs ADC is severed and thus the low battery check would
trigger immediately.

For making such devices still usable, add a config option to disable the
low battery check entirely.

Fixes: #227

See merge request !460

With sphinx 3 a ton of warnings about unresolvable xrefs are generated.
Add a workaround to silence them.

Ref: https://github.com/sphinx-doc/sphinx/issues/8945

Don't lint vendored sources...

Update vendored hawkmoth sources to commit upstream
69cde0b2c5315e46bf431a4c7c8b92cf47a544a6.

Use a newer container with Sphinx 3 installed.

fix(sdk): Prevent endless loop on I2C error

Closes #226

See merge request !465

The read operation needs to wait until the stop bit it sends on error is
handled. Otherwise a following write operation will loop.

Closes #226