Query imports: Manual cancellation

### Background The problem defined in https://github.com/grafana/grafana/issues/52213 Discussed in https://github.com/grafana/grafana/issues/55462 Solutions discussed in [design doc](https://docs.google.com/document/d/1n4niEjlB8cpfb4omzhHidc8XNHIQN0rixALDK9RrsTQ/edit#heading=h.5sybau7waq2q) ### Requirements ### High level: _Block the editor until the query is imported but allow cancelling the query manually_ #### Technical details Prerequisite: Refactor query imports to make them consistent across Explore / Dashboards / Alerting. ([comment](https://github.com/grafana/grafana/pull/62172)) TBD. #### To Do - [ ] Define technical details based on design doc - [ ] Check DoR TBD 🚧 Outstanding questions * ... <details><summary>DoR checklist</summary> - [ ] Should our squad work on it? ***TBD*** - [ ] Why is it important? ***TBD*** - [ ] Dependencies: ***TBD*** - [ ] Priority: ***TBD*** - [ ] Functional requirements. ***TBD*** - [ ] Non-functional requirements . ***TBD*** - [ ] Documentation requirements. ***TBD*** - [ ] UX design / approval. ***TBD*** - [ ] Technical design / approval. ***TBD*** - [ ] How will the outcome value of the feature be measured? ***TBD*** - [ ] Should we write a blog post about it? ***TBD*** </details>