to_edge_transform_and_lower (#3483)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/3483

This diff introduces the to_edge_transform_and_lower API. The changes introduces are:
- Adding support to the Parititioner class to register ops that it doesn't want to be composed
- Changes to _program.py to add the implementation of to_edge_transform_and_lower()
- Added a basic test case to test that Linear, SDPA & Linear + SDPA are not decomposed when asked and the corresponding backend consumes them.

Reviewed By: kimishpatel, mcr229

Differential Revision: D56401086

fbshipit-source-id: 04262a58fc70e8191df33b4342295e56a5baf354