simpleperf: remove synthesized D8/R8 frames.

In R8 mapping files, methods generated by the compiler are marked
with a synthesized comment. The synthesized methods are not useful
to be shown to developers. So remove them from call frames.

Bug: 263549058
Test: run simpleperf_unit_test
Change-Id: Iad85318436ae7db645de52d23bcb7f96db9d8f44
3 files changed