Add _MaybeCheckParamsDuringInitAfterTrialOverride to BaseRunner.
Add _MaybeCheckParamsDuringInitAfterTrialOverride to BaseRunner.

_MaybeCheckParamsDuringInitAfterTrialOverride, which in BaseRunner is a no-op, can be over-written by child classes to check class member variables after most variables are set and self._params gets modified by trial.OverrideModelParams.

Note that _MaybeCheckParamsDuringInitAfterTrialOverride is called after most major private variables are set, such as self._params, self._logdir, self._train_dir, etc.

Also slightly moved train directory creation to be called after _MaybeCheckParamsDuringInitAfterTrialOverride.

PiperOrigin-RevId: 475960504

tensorflow/lingvo,tensorflow/lingvo,tensorflow/lingvo,tensorflow/lingvo