micropython-lib: update to 1.28.0, add test.sh

micropython-lib: update to 1.28.0, add test.sh

micropython-lib is a companion repository to micropython, versioned in
lockstep. Both are now at 1.28.0 (released 2026-04-06).

The 001-build-unix-ffi.patch remains needed as the upstream has not yet
incorporated the --unix-ffi argument into the tools/build.py script.

test.sh:
- micropython-lib: verify stdlib-replacement modules (collections,
  functools, base64) can be imported via the /usr/lib/micropython path
- micropython-lib-unix: verify the micropython-unix wrapper script exists
  and that sqlite3/select are importable via the unix-ffi path

Signed-off-by: Alexandru Ardelean <redacted>