feat: allow plugins to add to admin cache list

[oplik0]

resolves #10820

plugins will have to use filter:admin.cache.get hook and just add their own cache to the object there.

Currently the template has a special case for configuring postCache size - however this could potentially be also made configurable, but since there isn't really a way to tell if that property is fixed, there would need to be a separate property for this (configurableSize?).

There is also now an easy way to add the caches that didn't make it to ACP before - blocks cache, ip cache (from analytics) and the two rate limiting caches (delayCache and the uploads rate limit cache). Please let me know if I should do so while I'm working with this :)

Additionally, TTLCache will only work partially, since the NodeBB wrapper doesn't expose max and size (which is renamed to itemCount in lru cache wrapper). This should be trivial to add, but I'm not sure if it's in scope of this PR (and wanted). If that's the case though I'll be glad to add this here too. Added these properties, along with dump, to the ttl cache wrapper

EDIT: an example implementation in a plugin can be seen here: https://github.com/oplik0/nodebb-plugin-two-way-block/tree/cache-metrics

[nodebb-misty]

💡 Friendly Note

This pull request was made against the develop branch, which is reserved for commits destined for a minor or major release.If your commits simply fixes a bug, please rebase this PR against the master instead.

• patch releases — bug fixes only
• minor releases — new features, enhancements, and bug fixes
• major releases — breaking changes, including all of the above

Thanks!