Codegen: Add root_name property to NativeFunction{,sGroup} (#68687)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68687
This adds `NativeFunction.root_name` which is the canonical name
for the operator group. i.e. the BaseOperatorName without inplace or
double-underscores. In the previous PR I referred to this as
`base_name` but confusingly `BaseOperatorName` does potentially
include inplace or double-underscores.
I also add the property to `NativeFunctionsGroup` so that grouped
functions with type `Union[NativeFunction, NativeFunctionsGroup]`
can have the property queried without needing `isinstance` checks.
Test Plan: Imported from OSS
Reviewed By: jbschlosser
Differential Revision: D32596271
Pulled By: albanD
fbshipit-source-id: 8b6dad806ec8d796dcd70fc664604670d668cae7
