SamplePGO - Clear per-function data after applying a profile.

SamplePGO - Clear per-function data after applying a profile.

The pass was keeping around a lot of per-function data (visited blocks,
edges, dominance, etc) that is just taking up memory for no reason. In
fact, from function to function it could potentially confuse the
propagator since some maps are indexed by line offsets which can be
common between functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251531 91177308-0d34-0410-b5e6-96231b3b80d8