[C2] Add TypeAndShape Inference logic for ReduceMean (#51828)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51828
As desc.
Test Plan: Unit-tests.
Differential Revision: D26293844
fbshipit-source-id: 2eb2a694c439b794ad7c134409e2b8926aabc91f
