Specify is_stubs_module property in selected aconfig library modules

"fake_device_config" and "strict_mode_stub" provide stubs and do not
contain any implementation details. Specifying the property
"is_stubs_module" to these modules allow inter-container dependency on
these modules.

Test: m nothing
Bug: 354029496
Change-Id: Ia65ad36ca02c0594fc753935f9cc7c0af6caa20d