refactor: move go-chi/cache into Gitea (#39530)

The `gitea.com/go-chi/cache` package only exists for Gitea, so it moves
into `modules/cache`.

- `ITEM_TTL = -1` disables caching as documented
- Sub-second TTLs round up instead of never expiring
- The Redis adapter no longer grows a `MacaronCache` hash
- Use two-queue cache for in-memory cache

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/cache/cache.go

@@ -13,8 +13,6 @@ import (
 
 	"gitea.dev/modules/setting"
 	"gitea.dev/modules/util"
-
-	_ "gitea.com/go-chi/cache/memcache" //nolint:depguard // memcache plugin for cache, it is required for config "ADAPTER=memcache"
 )
 
 var defaultCache StringCache
@@ -83,7 +81,7 @@ func GetCache() StringCache {
 
 // GetString returns the key value from cache with callback when no key exists in cache
 func GetString(key string, getFunc func() (string, error)) (string, error) {
-	if defaultCache == nil || setting.CacheService.TTL == 0 {
+	if defaultCache == nil || setting.CacheService.TTL <= 0 {
 		return getFunc()
 	}
 	cached, exist := defaultCache.Get(key)