fix(repo): correct mapping for domains (#10653)

This pull request fixes an issue where the repository would fail to scan
organization or instance structs if the `domains` column was `NULL`.

## Which problems are solved

If the `domains` column of `orgs` or `instances` was `NULL`, the
repository failed scanning into the structs. This happened because the
scanning mechanism did not correctly handle `NULL` JSONB columns.

## How the problems are solved

A new generic type `JSONArray[T]` is introduced, which implements the
`sql.Scanner` interface. This type can correctly scan JSON arrays from
the database, including handling `NULL` values gracefully.

The repositories for instances and organizations have been updated to
use this new type for the domains field. The SQL queries have also been
improved to use `FILTER` with `jsonb_agg` for better readability and
performance when aggregating domains.

## Additional changes
* An unnecessary cleanup step in the organization domain tests for
already removed domains has been removed.
* The `pgxscan` library has been replaced with `sqlscan` for scanning
`database/sql`.Rows.
* Minor cleanups in integration tests.

.github/workflows/core.yml

@@ -17,6 +17,7 @@ on:
 
 env:
   cache_path: |
+    backend
     internal/statik/statik.go
     internal/notification/statik/statik.go
     internal/api/ui/login/static/resources/themes/zitadel/css/zitadel.css*
@@ -43,7 +44,7 @@ jobs:
           continue-on-error: true
           id: cache
           with:
-            key: core-${{ hashFiles( 'go.*', 'openapi', 'cmd', 'pkg/grpc/**/*.go', 'proto', 'internal') }}
+            key: core-${{ hashFiles( 'go.*', 'openapi', 'cmd', 'pkg/grpc/**/*.go', 'proto', 'internal', 'backend/**') }}
             restore-keys: |
               core-
             path: ${{ env.cache_path }}