This is one of the many steps to commonize value profiling support between profile
runtime and compiler/llvm tools.
After this change, profiler runtime now can share the same C APIs to do VP
serialization/deseriazation with LLVM host tools (and produces value data
in identical format between indexed and raw profile).
It is not yet enabled in profiler runtime yet.
Also added a unit test case to test runtime profile data serialization/deserialization
interfaces implemented using common closure code.
llvm-svn: 254110