Migration Docs: Restructure plugin migration docs (#64900)

* initial restructuring

* add weights for ordering

* fix links

* remove aliases, add script

Co-authored-by: Jack Baldry <jack.baldry@grafana.com>
Co-authored-by: David Harris <david.harris@grafana.com>

* make pretty

* use correct link for angular to react guide

* refactor: move the migration guide to /Developers

* Revert "refactor: move the migration guide to /Developers"

This reverts commit 8f31af8dfd.

* fix: only redirect if the URL-hash has a valid redirect

* fix: use a rel-ref for the Angular-React migration guide link

* fix: update the hash redirects

---------

Co-authored-by: David Harris <david.harris@grafana.com>
Co-authored-by: Jack Baldry <jack.baldry@grafana.com>

docs/sources/developers/angular_deprecation.md

@@ -36,6 +36,6 @@ We encourage you to locate the repository of the corresponding plugin and create
 
 ### Links
 
-- [Migrate Angular to React](https://grafana.com/docs/grafana/latest/developers/plugins/migration-guide/#migrate-a-plugin-from-angular-to-react)
+- [Migrate Angular to React]({{< relref "./plugins/migration-guide/angular-react/" >}})
 - [Build a panel plugin](https://grafana.com/tutorials/build-a-panel-plugin/)
 - [Build a data source plugin](https://grafana.com/tutorials/build-a-data-source-plugin/)