fix(fabric): forward set_epoch to underlying sampler in DistributedSamplerWrapper (#21456)

The DistributedSamplerWrapper now forwards set_epoch() calls to the
underlying sampler if it supports the method. This fix is generic and
works for any sampler subclass that implements set_epoch(), not just
specific implementations.

This is important for samplers that use the epoch for shuffling or
other epoch-dependent behavior in distributed training.

Fixes #21454

Co-authored-by: Deependu <[email protected]>