west_commands: Fix parsing of extra args for test-item

An arg --test-item makes west loading twister's test configurations
form sample/testcase.yaml. It has to mirror twister's behavior.
It was not the case with "extra_args" section. Quotation  marks were
not removed in west as they were in twister. The quotation marks
have to be removed from the extra_args section but left in
extra_configs. The commit adds differentiation for those.

fixes: #60297

Signed-off-by: Maciej Perkowski <Maciej.Perkowski@nordicsemi.no>