[Alerting] disabling any within the code

[gmmorris]

Following up from discussion in our weekly sync:

Style guide recommend disabling explicit any within the code.
Disabling any reveals aprox. 400 error caused by changing any to unknown which means we're heavily relying on the lack of type checking - this has also revealed mistakes in unit tests, incorrectly typed uses of ES Query responses and a few smaller potentially mistaken usages of core APIs.

We should disabled the ability to explicit set any wherever possible, fix the mistakes and explicitly add an ignore where it is unavoidable.

This will include the following modules that represent around 200 uses of any:

1. alerting
2. alerting_builtin
3. actions
4. task manager
5. event log

Triggers UI causes aprox. 200 errors on its own so that will be handled in a subsequent PR.

[elasticmachine]

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