Disables logging and summaries of steps, steps/s, loss etc. when...

Disables logging and summaries of steps, steps/s, loss etc. when RunConfig.log_step_count_steps is None.

This is already how Estimator works (as one can see in line 2136 where we explicitly replace log_step_count_steps as None).  It should be backward compatible as current code would have crashed if log_step_count_steps is None.

PiperOrigin-RevId: 217019985