Make common cache typed with generics (#2896)

Making typed common cache so that we don't use wrong types
across set/get methods and more higher-level methods can be
defined for cache.
Currently, we are not able to operate over all keys of the cache
due to generic types.
I also removed code comments around the cache.

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/cache/cache_test.go

@@ -29,7 +29,7 @@ func checkErr(err error) {
 }
 
 func TestCache(t *testing.T) {
-	c := MakeCache(100*time.Millisecond, 100*time.Millisecond)
+	c := MakeCache[string, string](100*time.Millisecond, 100*time.Millisecond)
 
 	_, err := c.Set("a", "b")
 	checkErr(err)