Test changes to prepare for allowlist v2

This implements a number of in-place unit test changes to prepare for
some fundamental changes to bp2build ("allowlist v2"). This will change
bp2build so that rdeps of unconverted or missing modules will not be
converted by bp2build.

Bug: 301312260
Test: Unit tests
Test: Unit tests, with a local copy of allowlist v2 on
Change-Id: I8c8c0a24ba173e213fffcb0f8d7e99845705f4a7