PSv2: Replace existing `tf.distribute.experimental.ParameterServerStrategy` usage with `tf.compat.v1.distribute.experimental.ParameterServerStrategy` to prepare for the upcoming TF2 ParameterServerStrategy API release.
PSv2: Replace existing `tf.distribute.experimental.ParameterServerStrategy` usage with `tf.compat.v1.distribute.experimental.ParameterServerStrategy` to prepare for the upcoming TF2 ParameterServerStrategy API release.

The practically only difference for API endpoint switch is the monitoring from V2 to V1, for those who were using `tf.distribute.experimental.ParameterServerStrategy`. It's not supported in V2 and should be tracked as V1 anyway.

PiperOrigin-RevId: 334847114

google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research,google-research/google-research