feat(scalingengine): Support app annotation to disable autoscaling

[silvestre]

Background

During DevOps tasks such as deployments or periods where manual scaling is required (e.g., in an outage situation) a simple and quick way to disable autoscaling might be helpful that does not involve editing or deleting the autoscaling policy.

Details

This PR introduces an annotation app-autoscaler.cloudfoundry.org/disable-autoscaling. If it is set on an app the app-autoscaler will not scale it, even if a scaling policy is active. Instead an event is written to scaling history, referencing the annotation.

The annotation value should be used to document the reason why this annotation is set and will be reflected in the scaling history.

[sonarqubecloud[bot]]

Quality Gate failed

Failed conditions
37.3% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud

[silvestre]

The main commit is https://github.com/cloudfoundry/app-autoscaler-release/pull/2824/commits/84b078fd2d82e7e57ce684f244d4b9349979724c - the other changes are unrelated and could be split out to their own PRs if necessary.

[sonarqubecloud[bot]]

Quality Gate failed

Failed conditions
31.1% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud