[Stack Monitoring] improve unit tests in fetch functions in alerts

[neptunian]

After modifying all the ES queries in support of agent/integrations, we should have unit tests for how we except the query params to look. This PR adds them to the the alerts' fetch queries.

• Adds 2 assertions for each rule. That the query looks a certain way and that when CCS is disabled in config, the index pattern is updated to not perform cross cluster search.
• Updates the Missing Monitoring Data rule to have another term in the bool query filter of node_stats (see comment in code review)
• Update fetchClusters to use dataset: 'cluster_stats' that was missing even though we were including it in the index pattern (metrics-elasticsearch.cluster_stats-*)

[elasticmachine]

Pinging @elastic/infra-monitoring-ui (Team:Infra Monitoring UI)

[neptunian]

Since we are querying for metrics-elasticsearch.node_stats as part of the index pattern added here https://github.com/elastic/kibana/pull/119112/files#diff-666dd698bc0e64e0a8265f7f08b758b5d73921ea321e0312f32474e3f834ac9bR60, the term filter should have been added. I don't know why it didn't exist previously but probably because it used to look across many products before being changed to only look at ES. I presume adding the node_stats into the index pattern to begin with is correct and tested that the alert is still working.

[neptunian]

@elasticmachine merge upstream

[kibana-ci]

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Metrics [docs]

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
monitoring	35	39	+4

Total ESLint disabled count

id	before	after	diff
monitoring	39	43	+4

History

• 💚 Build #20528 succeeded 9058724
• 💚 Build #20447 succeeded cac65e8
• 💔 Build #20394 failed 42b8a62

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@elasticmachine merge upstream

cc @neptunian