Use AddReverseVariationDependency to avoid 1-variant fallback

Currently, reverse dependencies fallback to the only variant of a module
if only 1 variant exists, regardless of what the requested variations
were. This causes problems for the "base configuration" feature and
incremental soong, so properly specify the variant we want in the
apex vndk mutator.

Bug: 369916167
Test: m nothing --no-skip-soong-tests
Change-Id: I3e27c6a8a0b016c963a3c41aad1ce7953aa07e49