tests: Add some bytecode tests.

tests/bytecode/mp-tests/fun4.py

+def f(a, b=1, *c, d):
+    pass
+    #print(a,b,c,d) # bug in uPy!
+f = lambda a, b, *c, d: None # default arg
+#f = lambda a, b=1, *c, d: None # default arg for lambda not implemented

tests/bytecode/mp-tests/import6.py

+from . import bar
+from .. import bar
+from ... import bar
+from .... import bar
+from ..... import bar
+from ...... import bar
+from . import bar as abc
+from .foo import bar
+from ..foo import bar
+from ...foo import bar
+from .foo.bar import baz
+from ..foo.bar import baz
+from ...foo.bar import baz
+from .foo.bar import baz as abc