Revert "add an API for external backends to register custom device names (#86992)"
This reverts commit fb6826bfd82660aa905459f894c81d97d143dd2c.
Reverted https://github.com/pytorch/pytorch/pull/86992 on behalf of https://github.com/jeanschmidt due to breaking internal builds - D40534212 - arstudio-windows-tests-landcastle-0
