twister: config: test on integration plaforms if defined

Add option to force integration mode on a defined list of tests, for
example tests for sample that are identified with 'sample.'.

A sample per definition shall be tested on documented and supported
platforms listed in the sample documentation. Samples shall not be used
as tests to verify functionality of a feature on all available plaforms
in Zephyr.

To still allow testing on platforms not listed in the doc, and when such
platforms are covered by the provided filter, we should still be able to
build/run the tests on those platforms (not directly listed in
integration_platforms).

We detect a sample by its test identifier, i.e., it starts with 'sample.'.

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