Refactor PE so fusion specializations are configurable (#71650)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/71650
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Refactors PE so there is a current fusion strategy set, which will take in a vector of e.g. [(STATIC, 2), (DYNAMIC, 10)] which means fuse two static invocations then fuse 10 dynamic ones, then stop specializing.
Test Plan: Imported from OSS
Reviewed By: albanD
Differential Revision: D33801501
Pulled By: eellison
fbshipit-source-id: ebc7ac3c57e35a3b9bb15ab751f0aa1d25cc9bd5
(cherry picked from commit 8dd89088d3ceae800ea110d0b6949b759d4fe582)
