[NNC] Added matmul for NNC lowering/unified dtypes (#56456)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56456
Test Plan: Imported from OSS
Reviewed By: ZolotukhinM
Differential Revision: D27977532
Pulled By: Chillee
fbshipit-source-id: c04372d988c8ef795f27037348a155894c2eddad
