build: Default test modules to null-suite

The LOCAL_COMPATIBILITY_SUITE tag is used to package tests and
auto-generate test configs for use in the test infrastructure
and locally by atest.

Rather than update hundreds of makefiles across the tree, this
change adds significant atest support to many unittests.

Bug: 73000943, 72969679, 71510529
Test: `atest NotificationStressTests` works as expected.
Change-Id: I1b0a779b8366aee4b4df98181267f72fcb68916a