[12.x] Fix adding tags on new cache flush events

[AndrewMast]

Why

Alternative solution to #55157. Comes from discussion on #55142.

In #55121, Taylor said that the new CacheFlushed or CacheFlushing events should not extend CacheEvent. This makes sense since the CacheEvent is for events with a specific $key.

However, that means that we now have cache events that do not share a common ancestor and these events cannot have their tags set in TaggedCache (or RedisTaggedCache).

What

This PR attempts to fix this issue by adding a TaggedCacheEvent interface with a setTags method and making CacheEvent, CacheFlushing, and CacheFlushed implement it.

An alternative solution to this would be to allow CacheFlushing and CacheFlushed extend CacheEvent with an empty key (see #55157).

[GrahamCampbell]

I think most drivers don't support tags for flush, and just delete the entire cache.

[erikn69]

Great, let's wait for the review

[AndrewMast]

This honestly isn't a great implementation, and probably should be marked as a breaking change (even though its just a signature change). But then if we did that, we might as well make a breaking change to CacheEvent and move $key into a KeyedCacheEvent and have the other events extend it.

If a maintainer knows what way would make the most sense (and would be accepted), let me know and I could update this PR or create a new PR.

[taylorotwell]

Frankly I'm not sure what problem we are trying to solve here. I thought we just wanted events when the cache is flushing, which we now have.

[erikn69]

@taylorotwell hi, but on TaggableStore the flushed event is not firing
$cache->tags(['tag_key'])->flush(); // no event dispatched
$cache->tags(['tag_key'])->clear(); // bug on setTags

• Missing flushed cache event on Illuminate\Cache\TaggableStore #55101