This commit will not build, it exists just to track changes.

Preparing this to move to drivers/ directory, want to make it as similar
to original code from TI as possible.

This is how it should be, so one knows exactly where the includes are
coming from.

Saves around 1.3K. At the same time re-enable MICROPY_PY_SYS_EXIT
since it doesn't take much space and might be useful for certain
scripts.

Issue #1122 should now be fixed.

Disabling MICROPY_EMIT_INLINE_THUMB gives us back around 6K of
precious RAM.

I2C objects can be freed by the GC and a __del__ method is provided
in order to de-init the peripheral prior to being garbage collected.
UART objects are now added to a local list and this list is now part
of the VM_STATE.

Most of printing infrastructure now uses streams, but mp_obj_print() used
libc's printf(), which led to weird buffering issues in output. So, switch
mp_obj_print() to streams too, even though it may make sense to move it to
a separate file, as it is purely a debugging function now.

Relative imports are based of a package, so we're currently at a module
within a package, we should get to package first.

Also, factor out path travsering operation, but this broke testing for
boundary errors with relative imports. TODO: reintroduce them, together
with proper tests.

So corresponding exception can be thrown even under tight memory conditions.

Traceback allocation for exception will now never lead to recursive
MemoryError exception - if there's no memory for traceback, it simply
won't be created.

They are directly cast to str object, skipping allocation of formatting
buffer.

Has to be enabled by manual editing, but at least it's there, as debugging
NLR issues may be weird.

Pushing same NLR record twice would lead to "infinite loop" in nlr_jump
(but more realistically, it will crash as soon as NLR record on stack is
overwritten).

Conceptually it is part of code state, so let it be allocated in the same way
as the rest of state.