Release v12.2.0 tempest.lib interfaces

This Tempest has the following features as stable interfaces:
  - RestClient supports setting timeout in urllib3.poolmanager
  - KeystoneAuthProvider accepts http_timeout
  - Define identity service clients as libraries:
      endpoints_client(v3)
      policies_client (v3)
      regions_client(v3)
      services_client(v3)
      projects_client(v3)
  - ServiceClients class for the service clients which are in tempest.lib
  - A new optional interface TempestPlugin.get_service_clients
  - A new singleton class clients.ClientsRegistry
  - A new helper method service_client_config
  - Define volume service clients as libraries
      availability_zone_client(v1)
      availability_zone_client(v2)
      extensions_client(v1)
      extensions_client(v2)
      hosts_client(v1)
      hosts_client(v2)
      quotas_client(v1)
      quotas_client(v2)
      services_client(v1)
      services_client(v2)
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