Revert "Revert "[ProfileData] Read and symbolize raw memprof profiles.""

This reverts commit dbf47d22.

Reapply https://reviews.llvm.org/D116784 now that
https://reviews.llvm.org/D118413 has landed with a couple of fixes:
* fix raw profile reader unaligned access identified by ubsan
* fix windows build by using MOCK_CONST_METHOD3 instead of MOCK_METHOD.