Alerting APIs fail when alert fails to be decrypted

[mikecote]

There's a few scenarios where we load the decrypted alert before performing an action. In those scenarios, it's trying to load the previous API key to invalidate it after a new one has been assigned. If the decryption fails (AAD), the API currently fails and shouldn't.

APIs that currently fail:

• delete (Ability to delete alerts even when AAD is out of sync #56543)
• enable / disable (Fix enable and disable API to still work when AAD is out of sync #56634)
• update (Fix update alert API to still work when AAD is out of sync #57039)
• update api key (Make the update alert API key API work when AAD is out of sync #56640)
• follow up on delete PR Ability to delete alerts even when AAD is out of sync #56543 (comment) (Load alert on delete with a fallback instead of doubling the calls (ESO + SOC calls) #57004)

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[mikecote]

Closing issue now that all the sub-PRs are merged.