Flatten service context on template evaluation

Template evaluation function "context" for services flattens all ancestors'
contexts into a single map.
Add contextFilter template evaluation function

contextFilter only returns context items whose key matches the prefix and
removes the prefix from the key
Master monitors changes in its own realm
Merge pull request #981 from control-center/feature/ZEN-10755

Add inherited, filtered context to service template evaluation
Merge pull request #983 from control-center/feature/realmsync-2

Master monitors changes in its own realm
Merge remote-tracking branch 'origin/develop' into feature/CC-54