This CL moves `internal::Framework`, `internal::TestInfo`, and `State`
out of pw_perf_test.h and into their own separate files.
It also moves performance_test_generic.cc to
examples/example_perf_test.cc.
Finally, it removes perf_test_test.cc as this file created a no-op unit
test.
Change-Id: Id5e984cdf80bb7ed801be1f81ebb8cba8c05b91b
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/178914
Reviewed-by: Armando Montanez <amontanez@google.com>
Commit-Queue: Aaron Green <aarongreen@google.com>
