give "validation sanity check" flag for "validation_epoch_end" & "validation_step"
🚀 Feature
Motivation
When using some custom saver, logger in validation function (validation_epoch_end, validation_step), with Trainer.fit(), it always execute validation sanity check so mess log comes out.
Pitch
def validation_step(self, batch, batch_nb, sanity_check):
   if sanity_check:
      ...
def validation_epoch_end(self, outputs, sanity_check):
   if sanity_check:
      ...
or
def validation_step(self, batch, batch_nb):
   if self.sanity_check:
      ...
def validation_epoch_end(self, outputs):
   if self.sanity_check:
      ...
Alternatives
None
Additional context
None