Ability to retain specialised pods for poolmanager functions (#2830)

- added retainPods flag to take in the number of specialized pods to retain
- add retainPods in both the create function and update function command
- modify crd keys to be typed instead of string
- keep track of function generation in case of update function operation
- add delete handler function to make sure specialized pods are deleted in case function is deleted

---------

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>
Signed-off-by: Pranoy Kundu <pranoy1998k@gmail.com>
Co-authored-by: Pranoy Kundu <pranoy1998k@gmail.com>

pkg/router/functionHandler.go

@@ -684,7 +684,7 @@ func (fh functionHandler) getServiceEntry(ctx context.Context) (svcURL *url.URL,
 
 	fnMeta := &fh.function.ObjectMeta
 	recordObj, err := fh.svcAddrUpdateThrottler.RunOnce(
-		crd.CacheKey(fnMeta),
+		crd.CacheKeyURFromMeta(fnMeta).String(),
 		func(firstToTheLock bool) (interface{}, error) {
 			if !firstToTheLock {
 				svcURL, err := fh.getServiceEntryFromCache()