Reland of "D27708346: generate xla codegen in-tree" (#56601)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56601
Updating it to ensure that RegistrationDeclarations.yaml is completely
unchanged
This reverts commit 90e532f3ef17a9611e9e7a9f1f6189d4168bf084.
Test Plan: Imported from OSS
Reviewed By: ailzhang
Differential Revision: D27915305
Pulled By: bdhirsh
fbshipit-source-id: 491a025c44221690dad849f9a2166934130c0fec
