CODEOWNERS: Remove Andrzej Puzdrowski from most maintainerships

Andrzej is no longer involved directly in Zephyr, but remains connected
to the MCUboot project. Replace his maintainership with either other
people from Nordic or leave the subsystem "orphaned" (i.e. labeled as
odd fixes).

Also add @nordicjm to the SMP/MCUmgr maintainership, as he is already an
SMP/MCUmgr collaborator.

Finally, removed @aunsbjerg from mcumgr path maintainership, since he's
already assigned to the UDP platform implementation, which is what he is
an owner of.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>