Overhaul ContentCacheFlusher

[dlubitz]

At the moment the ContentCacheFlusher can't flush caches discarded nodes. This seems to be caused by the fact, that after persisting the change (discard), the ContentCacheFlusher tries to identify his parents, which is not possible anymore.

To solve this issue, we need to do all node traversing operation BEFORE the persistence. Which should be done in the GraphProjectorCatchUpHookForCacheFlushing. So the ContentCacheFlusher does not need to do any node traversing anymore and simply flush all given caches.

Currently this doesn't have a effect, as the cacheEntryIdentifier is based on the contentStreamId, which leads to orphan cache entries after each new contentStream creation. On the other hand, the cache entry is not used anymore after discard, which means the same as a cache flush of the entry.

See also:

• https://neos-project.slack.com/archives/C04PYL8H3/p1718800219964049
• BUG: Discarded node remains in cache if UI was reloaded between creation and discard #5150
• BUGFIX: Fix content cache for discard, revert #5083 for now #5163
• WIP: BUGFIX: Flush content cache on discard #5155
• WIP 5150 flush content cache correctly #5160