[Caching] Deprecate cacheMetaExtension(), report warning when used

[TomasVotruba]

The cacheMetaExtension() is a niche mechanism. Let Rector handle its cache on its own; if custom invalidation is needed, CI can handle it in a more generic way, e.g. by clearing the cache directory.

The config option stays and is marked @deprecated; it only reports a warning now. The mechanism itself is no longer applied, so there is no BC layer to keep alive.

What is deprecated

• RectorConfig::cacheMetaExtension()
• RectorConfigBuilder::withCacheMetaExtension()
• CacheMetaExtensionInterface

Warning on use

return RectorConfig::configure()
    ->withRules([...])
    ->withCacheMetaExtension(SomeCacheMetaExtension::class);

  [OK] Rector is done!
+
+ [WARNING] Cache meta extension "SomeCacheMetaExtension" is deprecated and no
+           longer applied. It is a niche mechanism, let Rector handle cache on
+           its own. If custom invalidation is needed, handle it in CI in a more
+           generic way, e.g. by clearing the cache directory.

Docs removal: https://github.com/rectorphp/getrector-com/pull/new/remove-cache-meta-extension-docs

[ruudk]

Hi Tomas, by luck I stumbled upon this PR that removes my work from #7933. Of course I'm a bit sad to see this but it's your call after all which I respect.

I see you don't see a need for cache extensions. Would you be open for allowing configuring a custom FileComputeHasher? Then I could just override the hash method with my custom logic.

Moving this cache busting responsibility to the CI as suggested in this PR is not really an option for when using it locally.

[TomasVotruba]

Hey, sorry to hear that. I'm trying to make Rector more and more simpler and cutting niche features. Saying that, won't accept any such feature: I'd be open to those benefiting most users and general Rector speed.
I suggest using a wrapper caching tool that would handle your specific need.