Move BackendSelect to default_included_set. (#55117)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/55117
Test Plan: Imported from OSS
Reviewed By: bhosmer
Differential Revision: D27490571
Pulled By: ailzhang
fbshipit-source-id: a0d8a25a8217a754061fbf3b8e31cc1cf2d3bdea
