PloneRestApiDXPAMLayer and PloneRestApiDXIterateLayer duplicate ~95% of the setup that PloneRestApiDXLayer already provides, each triggering a redundant ZCML + GenericSetup profile loading cycle.

Fix: Make both layers extend PLONE_RESTAPI_DX_FIXTURE instead of building standalone stacks. The PAM layer only needs to add plone.app.multilingual:default on top. The Iterate layer only needs to add iterate ZCML + profiles on top.

Also switch test_boolean_value.py and test_indexers.py from FUNCTIONAL to INTEGRATION testing (they never make HTTP calls or commit transactions).

Result: all specialized layers share one base, saving ~5-15s of redundant layer setup per test run.