fix(eventstore): cleanup org fields on remove (#8946)

# Which Problems Are Solved

When an org is removed, the corresponding fields are not deleted. This
creates issues, such as recreating a new org with the same verified
domain.

# How the Problems Are Solved

Remove the search fields by the org aggregate, instead of just setting
the removed state.

# Additional Changes

- Cleanup migration script that removed current stale fields.

# Additional Context

- Closes https://github.com/zitadel/zitadel/issues/8943
- Related to https://github.com/zitadel/zitadel/pull/8790

---------

Co-authored-by: Silvan <silvan.reusser@gmail.com>

cmd/setup/39.go

@@ -0,0 +1,27 @@
+package setup
+
+import (
+	"context"
+	_ "embed"
+
+	"github.com/zitadel/zitadel/internal/database"
+	"github.com/zitadel/zitadel/internal/eventstore"
+)
+
+var (
+	//go:embed 39.sql
+	deleteStaleOrgFields string
+)
+
+type DeleteStaleOrgFields struct {
+	dbClient *database.DB
+}
+
+func (mig *DeleteStaleOrgFields) Execute(ctx context.Context, _ eventstore.Event) error {
+	_, err := mig.dbClient.ExecContext(ctx, deleteStaleOrgFields)
+	return err
+}
+
+func (mig *DeleteStaleOrgFields) String() string {
+	return "39_delete_stale_org_fields"
+}