Add api for changing function executor settings, hook up execution with decomposition registry (#74186)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74186
Make the execution settings mutable on function_impl so that we can set it for running op decompositions. Add mapping to function objects and show example in test of executing op decompositions.
Test Plan: Imported from OSS
Reviewed By: gchanan
Differential Revision: D34938125
Pulled By: eellison
fbshipit-source-id: adf108b2f6c1bd166910c6d7b94245661d67ce0d
(cherry picked from commit 9957e33803002d9e71abe4ff802769270b6960d3)
