Add back compat config for RUN_NATIVE_NSD_ONLY_IF_LEGACY_APPS, which was
lost when moving NsdManager to framework-connectivity-t.
This causes NsdManager to start mdnsresponder again when used by apps
with target SDK < 31.
The change also changes the compat ID used, to make sure it does not
conflict with the ID already in use in S and below, when the module is
installed on such a platform. This is the only ChangeId used by
framework-t.
Also add a CtsNetTestCasesMaxTargetSdk30 test to verify that behavior.
Bug: 235355681
Test: atest CtsNetTestCasesMaxTargetSdk30
Change-Id: I7ca6051d0a4ba5aff3e44bece2cbac22eb1be32d
348bbb0231