MDEV-26142: Fix failures of the tests main.features and sys_vars.stored_program_cache_func when they are run in PS mode

These tests produced different results in case they were run
with the option --ps-protocol.

These tests produced different result sets since a value of
Feature_subquery and handler_read_key status system variables
are updated one time more for ps-protocol (the first time it is updated
on Prepare phase and the second time on Execute phase of PS protocol)
So different result sets are expected for both tests. To make tests
successfully runnable both for case it is run with and without
the option --ps-protocol the new protocol combination [ps, nm]
and protocol specific result files have been added.

Moreover, the perl script mysql-test/mariadb-test-run.pl
has been updated to make the variable opt_ps_protocol visible
outside perl file containing this variable.