Migrate v2022_01_01_preview consumers to shared arm_ml_service client

Move the workspace-connection auth models off the per-version v2022_01_01_preview
package onto the shared arm_ml_service client and delete the package.

- entities/_credentials.py: re-source the workspace-connection auth models from
  arm_ml_service with their current (renamed) names:
  PersonalAccessToken -> WorkspaceConnectionPersonalAccessToken,
  ServicePrincipal -> WorkspaceConnectionServicePrincipal,
  SharedAccessSignature -> WorkspaceConnectionSharedAccessSignature,
  UsernamePassword -> WorkspaceConnectionUsernamePassword,
  ManagedIdentity -> WorkspaceConnectionManagedIdentity.
- Cross-version coupling fix: the compute identity (IdentityConfiguration
  _to_compute_rest_object / _from_compute_rest_object, used by aml/compute_instance/
  kubernetes/synapsespark compute) is serialized through the msrest v2022_10
  ComputeResource. Source those two models from v2022_10_01_preview msrest instead
  of arm_ml_service so msrest serialization keeps working:
  Identity -> v2022_10_01_preview.ManagedServiceIdentity (same fields), and
  UserAssignedIdentity -> v2022_10_01_preview.UserAssignedIdentity. Without this the
  hybrid models raise SerializationError ('object has no attribute _attribute_map').
- Update conftest mock fixture and the connection unit test to import from
  arm_ml_service.
- Delete the now-unused azure/ai/ml/_restclient/v2022_01_01_preview/ package.

Author: saanikaguptamicrosoft