twister: only parse specified tests when using --test

Enhance the -s option of twister, used to point to a single scenario in
a testsuite.
- Now accept --scenario on the command line, --test still supported.
- If no testsuite is provided, extract testsuite from scenario
  identifier and avoid parsing the whole tree if we only want to address
  one scenario in a testsuite.
- If just the identifier of the scenario is provided to
  --test/--scenario option, try to find this as well, do not need the
  full path for that.

Something like this is now possible:

twister  --scenario kernel.threads.init --list-tests
twister -T <path> --scenario kernel.threads.init --list-tests
twister -T <path>/kernel.threads.init --list-tests

All should print the same output.

Fixes #67307

Signed-off-by: Anas Nashif <anas.nashif@intel.com>