kube-controller-manager: add ResourceClaim controller

The controller uses the exact same logic as the generic ephemeral inline volume
controller, just for inline ResourceClaimTemplate -> ResourceClaim.

In addition, it supports removal of pods from the ReservedFor field when those
pods are known to not need the claim anymore. At the moment, only this special
case is supported. Removal of arbitrary objects would imply granting full read
access to all types to determine whether a) an object is gone and b) if the
current incarnation is the one which is listed in ReservedFor. This may get
added later.

pkg/controller/resourceclaim/uid_cache.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package resourceclaim
+
+import (
+	"sync"
+
+	"github.com/golang/groupcache/lru"
+
+	"k8s.io/apimachinery/pkg/types"
+)
+
+// uidCache is an LRU cache for uid.
+type uidCache struct {
+	mutex sync.Mutex
+	cache *lru.Cache
+}
+
+// newUIDCache returns a uidCache.
+func newUIDCache(maxCacheEntries int) *uidCache {
+	return &uidCache{
+		cache: lru.New(maxCacheEntries),
+	}
+}
+
+// Add adds a uid to the cache.
+func (c *uidCache) Add(uid types.UID) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	c.cache.Add(uid, nil)
+}
+
+// Has returns if a uid is in the cache.
+func (c *uidCache) Has(uid types.UID) bool {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	_, found := c.cache.Get(uid)
+	return found
+}