Make Meta into a backend component
Seems like it should be one. This will make it possible to register
meta implementations even when there is a CompositeImplicitAutograd
registration already. It also paves the way for sparse meta, etc.
Signed-off-by: Edward Z. Yang <ezyangfb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/78469
Approved by: https://github.com/ngimel
