Delete CacheLayer

[zepumph]

Since adding a new Transpiler, we have some buggy code with CacheLayer I believe. It doesn't know when to break the cache for pre-commits. @samreid is this right?

[zepumph]

I'm more scared about it this now, because I really don't want to expose the need to regenerate all phet-io APIs for each repo. It seems like that cacheing, for multiple pre-commit tasks run in a row, is still working. Perhaps we need to keep that feature?

[samreid]

Some thoughts, no particular order:

1. I would prefer not to have a watch process that invalidates caches
2. I would prefer not to try to leverage the SWC watch process for caching
3. Adding a new cache strategy like "did this test already pass within 5 minutes" could be buggy, and could "kick off" multiple tests at once if precommit hooks run in parallel anyways.
4. We recently got a speed boost in generating phet-io apis by caching in the web server layer.
5. We already opt out of testing when running in phet-io-sim-specific itself.
6. Pre-commit tests are supposed to be fast and independent. I believe that a more sophisticated "multi-repo-aware" strategy is the correct solution to this problem. But I do not know how developers could make that automatic.

Let's discuss