Mark alpha/beta classes with `@deprecated` when a stable version exists

Deprecate alpha / beta clients (e.g. `v1beta1` [Firestore](https://cloud.devsite.corp.google.com/php/docs/reference/firestore/latest/V1beta1.ArrayValue)) by adding `@deprecated` to the GAPIC client classes (and potentially all classes) with the logic that "if `Vn` exists, then `Vn(\w+)` should be marked as deprecated". e.g.:

- `Asset\V1` and `Asset\V1beta1`
- `AutoMl\V1` and `AutoMl\V1beta1`
- `BillingBudgets\V1` and `BillingBudgets\V1beta1`
- `DataprocMetastore\V1`, `DataprocMetastore\V1alpha`, and `DataprocMetastore\V1beta`
- `Firestore\V1` and `Firestore\V1beta1`
- `Language\V1` and `Language\V1beta2`
- `ManagedIdentities\V1` and `ManagedIdentities\V1beta1`
- `Memcache\V1` and `Memcache\V1beta2`
- `OsLogin\V1` and `OsLogin\V1beta`
- `Redis\V1` and `Redis\V1beta1`
- `Scheduler\V1` and `Scheduler\V1beta1`
- `SecretManager\V1` and `SecretManager\V1beta1`
- `SecurityPrivateCa\V1` and `SecurityPrivateCa\V1beta1`
- `SecurityCenter\V1` and `SecurityCenter\V1p1beta1`
- `ServiceDirectory\V1` and `ServiceDirectory\V1beta1`
- `Speech\V1` and `Speech\V1p1beta1`
- `Talent\V4` abd `Talent\V4beta1`
- `Tasks\V2`, `Tasks\V2beta2` and `Tasks\V2beta3`
- `WebRisk\V1` and `WebRisk\V1beta1`
- `VideoIntelligence\V1` and `VideoIntelligence\V1beta2`
- `VideoTranscoder\V1` and `VideoTranscoder\V1beta1`