llvm-profdata: Use the Profile library, implement show and generate

llvm-profdata: Use the Profile library, implement show and generate

This replaces the llvm-profdata tool with a version that uses the
recently introduced Profile library. The new tool has the ability to
generate and summarize profdata files as well as merging them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203704 91177308-0d34-0410-b5e6-96231b3b80d8