[Breaking Changes] Fail if an existing tag is updated to a different swagger version

In this PR, an existing tag `package-2025-04-01` was updated to include `2025-03-03/GalleryRP.json` instead of `2024-03-03/GalleryRP.json`.

https://github.com/Azure/azure-rest-api-specs/pull/38715/files/211ea1f728e3c34a24e466f84e0220734e0fbef1?new_files_changed=true#diff-5871f1ff4953a3d11f8779e01460fe0ae3cb27630c3868c55a53417859e83a0aR363

This **should** have caused an error from one of our breaking changes checks, but it did not. Likely because our checks currently work on the level of **individual swagger files**, not **api versions which contain multiple swagger files**.

Also, check "Swagger Avocado" does flag this PR with `MULTIPLE_API_VERSION`. Once this spec is migrated to "folder structure v2", the problem may go away, since API versions should align with swagger versions.