micropython: Update to 1.21.0, refresh/redo patches

micropython: Update to 1.21.0, refresh/redo patches

Removed 050-py-stackctrl-fix-gcc-13.patch as it has been merged in the
new version.

This also:

* Add STRIP= (empty value) to skip micropython's stripping step, letting
  the OpenWrt build system control stripping.

* Add a workaround for "variable might be clobbered" warning leading to
  build error on riscv64
  (https://github.com/micropython/micropython/issues/12838).

* Change Build/InstallDev to install host tools into an unversioned
  directory, and update micropython-lib to use the unversioned path.
  There is no need to keep available multiple versions of the host
  tools.

* Add a test.sh script for the packages feed CI.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>