Write ELF symbol binding to abidiff

ConvertElfFunctionIR converts symbol binding to protobuf so that
ProtobufIRDiffDumper writes it to the abidiff. Besides, this commit
moves some function implementations from converter.h to ir_dumper.cpp.

Test: ./test.py
Bug: 323447559
Change-Id: I1176a17683ce2d70195c2b563d8943e4164d4114
4 files changed