[export] Add run_decomposition() function to ExportedProgram (#110236)
Summary:
https://docs.google.com/document/d/1QJJEGnj2nHGPODlw38BEG3KLLCOTfdOVjPrNQbz_LM8/edit#bookmark=id.lp80wfshq130
`exported_program.run_decompositions(decomposition_table)` will optionally take a decomposition table, and run decompositions on the exported program, returning a new exported program. By default we will run the Core ATen decomposition table.
Splitting up this diff with the following one (D49742989) to make migrating Executorch easier:
1. Land this diff
1. Wait for a pytorch nightly to include this diff
1. Update executorch's pytorch nightly
1. Land the following diff to have export() return no decomps
Test Plan: Tested in following diff
Differential Revision: D49743208
Pull Request resolved: https://github.com/pytorch/pytorch/pull/110236
Approved by: https://github.com/gmagogsfm