roll: pigweed pw_compilation_testing: Consolidate generic (non-GN) functionality

- Move more code into the generic enumerate_tests and run_test functions
  to prepare for a Bazel implementation.
- Only check if a test is disabled if compilation succeeds. This speeds
  up tests since it removes a preprocessor invocation from most tests.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/322873
Original-Revision: 2c0b581240be92bda0d6377a0e3a74f800c75406

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: a764d26aefecc6..2c0b581240be92
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8703426805973555057
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Change-Id: I6f626edd5d22a12de3883b49af1c4aa24febe434
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/showcase/sense/+/323516
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