[Relay][Op] embedding_bag operator implementation

[juda]

trafficstars

This PR adds a new operator that supports embedding_bag operator similar to torch.embedding_bag.

Co-Authored-By: Masahiro Masuda [email protected] @shingjan @yelite

cc @blackkker

[shingjan]

I took a quick look and this PR should be in pretty good shape after CI is fixed.

cc: @masahi Can you also take a look at this? Would really appreciate your review on this. Thanks!

[juda]

@tvm-bot rerun

[shingjan]

@areusch this should be closed by #12993