Convert trivial TopDown mutators to BottomUp

Many TopDown mutators can be easily converted to BottomUp mutators,
which are easier to handle for incremental and partial analysis.

Bug: 367784740
Test: all soong tests pass
Test: no change to build.ninja
Flag: EXEMPT refactor
Change-Id: I82955e844ed0eb6680854678c0744ac5398eb7ba