<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Removes deprecated symbols from `extensionauth` and `configauth` modules
<!-- Issue number if applicable -->
#### Link to tracking issue
Follows #12574
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Adds errors in return type to `extensionauth.New*` functions. This is
not a breaking change since `extensionauth` is an unreleased module.
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
- Deprecates `extension/auth` in favor of `extension/extensionauth`.
- Deprecates `extension/auth/authtest` in favor of
`extension/auth/authtest`
Pablo Baeyens