GraphQL API: Create a new API to "Reset registration token" for runners

Description

As part of #329658 (closed) we should migrate the entire UI to use GraphQL APIs.

We should offer a way for users to reset the token programmatically via the GraphQL API.

Detailed API spec

TBD, in workflowsolution validation

Other considerations

• Owners and maintainers of both Groups and Projects should also be able to reset their Registration tokens, so the API should be extensible to cover those cases.