[alert_generator] Add test case covering ordered rules and producing more alerts after a delay.

[codesome]

• Rule that produces new alerts that go from pending->firing->inactive while already having active alerts.
• A rule group having rules which are dependent on the ALERTS series from the rules above it in the same group.
• Expansion of template in annotations only use the labels from the query result as source data even if those labels get overridden by the rules. They do not use the rules' additional labels.