[8.9] [Synthetics] Fixed action connectors and added api test for default alerting (#161218)

[shahzad31]

Backport

This will backport the following commits from main to 8.9:

• [Synthetics] Fixed action connectors and added api test for default alerting (#161218)

Questions ?

Please refer to the Backport tool documentation

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[apmmachine]

🤖 GitHub comments

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Just comment with:

• /oblt-deploy : Deploy a Kibana instance using the Observability test environments.
• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 77ba54e

Metrics [docs]

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	13	15	+2
securitySolution	415	419	+4
total			+6

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	14	16	+2
securitySolution	496	500	+4
total			+6

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[awahab07]

LGTM