[memprof] Refactor tests to generate binaries and profiles on the fly.

This change replaces the binary profiles and executables used for
testing the memprof profile reader with tests where the profiles are
generated on the fly. This reduces toil when the profile version
changes. The tests are moved from tools/llvm-profdata to
compiler-rt/test/memprof due to the following reasons:
1. Adding dependency on memprof lit.cfg.py for llvm-profdata is
   preferable to adding a dependency on compiler-rt for llvm/test.
2. All the tests can now be run with `ninja check-memprof`.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D145023