Remove IRDiffToProtobufConverter

IRDiffToProtobufConverter contains static functions only. They are
moved to ir_diff_dumper.cpp.

Test: ANDROID_BUILD_TOP=`realpath .` \
      PATH=$PATH:`realpath out/soong/dist/bin` \
      development/vndk/tools/header-checker/tests/test.py
Bug: 323447559
Change-Id: If8f521fa511b6900e099b1253610c1459de01b51
4 files changed