## Summary
This PR adds `as_<group>` methods to `AnyNodeRef` to e.g. convert an
`AnyNodeRef` to an `ExprRef`.
I need this for go to definition where the fallback is to test if
`AnyNodeRef` is an expression and then call `inferred_type` (listing
this mapping at every call site where we need to convert `AnyNodeRef` to
an `ExprRef` is a bit painful ;))
Split out from https://github.com/astral-sh/ruff/pull/16901
## Test Plan
`cargo test`