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/setting/cache_test.go

@@ -69,3 +69,14 @@ ADAPTER = memcache
 		})
 	}
 }
+
+func TestCacheItemTTLSeconds(t *testing.T) {
+	defer test.MockVariableValue(&CacheService)()
+	for ttl, want := range map[string]int64{"-1": -1, "500ms": 1} {
+		cfg, err := NewConfigProviderFromData("[cache]\nITEM_TTL = " + ttl + "\n[cache.last_commit]\nITEM_TTL = " + ttl)
+		assert.NoError(t, err)
+		loadCacheFrom(cfg)
+		assert.Equal(t, want, CacheService.TTLSeconds())
+		assert.Equal(t, want, LastCommitCacheTTLSeconds())
+	}
+}