llvm-profdata: Use consistent file suffixes in tests

In some places we've been using different suffixes for the different
file formats involved in instrprof, but in others we've just
ambiguously used .profdata. Update the test files to indicate the
types of file more obviously.

No functional change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214357 91177308-0d34-0410-b5e6-96231b3b80d8