Adjust dependencies/code for doctrine/annotations 2 compatibility

[demiankatz]

This PR is work in progress on addressing #800.

TODO

• [x] Resolve cache-related issues
• [x] Test with doctrine/annotations 1.x after finishing code changes to see if backward-compatibility is maintained, or if we need to fully bump the required version

[greg0ire]

Regarding the cache, there is already an issue about this it seems: https://github.com/doctrine/DoctrineModule/issues/786

[demiankatz]

Thanks, @greg0ire -- in fact, it looks like there's work in progress at #796.

[demiankatz]

I did some experimentation with merging together this PR and #786, but it still doesn't work -- I've left some more detailed comments on #786 since I think it might make sense to try to get the cache updates done before tackling this part.

[demiankatz]

@greg0ire, I found a little more time to work with this further today, and I've gotten this into a state that passes all tests with both annotations v1 and annotations v2. However, when using annotations v2, caching functionality is going to be lost (for now) because the cache objects do not comply with PSR-6. However, I believe this is written in such a way that if we return PSR-6 compliant objects in future, the caching will begin to work -- I'm not sure if #796 can help with that.

Obviously, as noted earlier, I don't have a deep understanding of this module, so it's possible I'm overlooking something important... but hopefully passing tests are a good first step. Please let me know if there's more I can do to help! I've taken this PR out of draft mode so that it can be reviewed.

[demiankatz]

In reviewing #800, I was reminded that @andremartinez was encountering phpstan failures. I was able to reproduce the problem and found that it was caused by referencing a non-existent (legacy) Blackhole cache adapter in a test. The easiest solution was to simply skip the test if the newer, expected version of the adapter was missing. I'm not seeing any skipped tests when I run the suite in my environment, so I think this is probably safe for now, especially since things are going to be significantly revised by #796 when that work is completed.

[demiankatz]

Apologies, I see that my phpstan fix broke the styles. Everything should be corrected now!

[demiankatz]

Thanks, @greg0ire!

[demiankatz]

Thanks, @andremartinez! It may make sense to finish the cache related work before addressing the test coverage warnings. Some lines may not be reachable until that's done, and others may become obsolete. Let me know if I can do more to help, in any case!

[TomHAnderson]

The order of PRs Dennis and I are shooting for is

799

801

796

@driehle Are you back and ready for #799?

[demiankatz]

Thanks, @TomHAnderson, let me know if I can do anything else to help (either in terms of contributing to #799, or in terms of improving test coverage in a new PR after #796 is merged). My time is going to be pretty limited for the next couple of weeks, but if I plan ahead, I can help out a little down the road. :-)

[TomHAnderson]

In the interest of moving this forward I've deprioritized #799 at this time though I expect to merge it before a release is made.