simpleperf: Don't remove r8 synthesized frames by default

Because some synthesized methods are generated via Horizontal
Class Merger optimization from R8. These frames may still
be useful to users.

Also add env variable REMOVE_R8_SYNTHESIZED_FRAME to control
removing synthesized frames. So we can try its effect.

Bug: 263549058
Test: run simpleperf_unit_test
Change-Id: I30ba6b65f0c23c7f0c7b482e623087fceafeb579
3 files changed