Remove the v1alpha1 version of the Observability API

[salonichf5]

We need to remove v1alpha1 version of the Observability API in the future. We are supporting a newer version v1alpha2 for Observability API now.

PR to support the newer version.

Note:

• We should wait 3 releases after 1.6 before removing v1alpha1.

[mpstefan]

We may not need to do this when considering our strategy for updating CRDs.

[salonichf5]

We will not bump the version of ObservabilityPolicy CRDs to add the validation of minimum one target ref.

[bjee19]

Re-opened this issue and changed the referenced PR to the new one bumped the API version and requires this task.