fix(backend): memory leak in memory caches (#14363)

* encapsulate `MemoryKVCache<T>`

* remove infinity caches

* encapsulate other caches

* add missing awaits to internally synchronize caches

* implement pull-through caching

* tune cache lifetimes

* optimize cache GC by stopping early

* summarize changes in CHANGELOG.md

* Fix timeout comments

Co-authored-by: かっこかり <67428053+kakkokari-gtyih@users.noreply.github.com>

* add comments about awaiting the redis write

---------

Co-authored-by: かっこかり <67428053+kakkokari-gtyih@users.noreply.github.com>

packages/backend/src/server/api/AuthenticateService.ts

@@ -37,7 +37,7 @@ export class AuthenticateService implements OnApplicationShutdown {
 
 		private cacheService: CacheService,
 	) {
-		this.appCache = new MemoryKVCache<MiApp>(Infinity);
+		this.appCache = new MemoryKVCache<MiApp>(1000 * 60 * 60 * 24 * 7); // 1w
 	}
 
 	@bindThis