DEV: Prepare new structure for migrations-tooling (#26631)

* Moves existing files around. All essential scripts are in `migrations/bin`, and non-essential scripts like benchmarks are in `migrations/scripts`
* Dependabot configuration for migrations-tooling (disabled for now)
* Updates test configuration for migrations-tooling
* Shorter configuration for intermediate DB for now. We will add the rest table by table.
* Adds a couple of benchmark scripts
* RSpec setup especially for migrations-tooling and the first tests
* Adds sorting/formatting to the `generate_schema` script

.github/dependabot.yml

@@ -81,3 +81,11 @@ updates:
       types:
         patterns:
           - "@types/*"
+#  - package-ecosystem: "bundler"
+#    directory: "migrations/config/gemfiles/convert"
+#    schedule:
+#      interval: "weekly"
+#      day: "wednesday"
+#      time: "10:00"
+#      timezone: "Europe/Vienna"
+#    versioning-strategy: "increase"