Unified: Run resource data migrations at startup (#114857)

* chore: uncomment unified migration

* chore: adapt and fix tests

* chore: dynamically bump max conns if needed during migration

* chore: copilot suggestions

* chore: pass ctx in RegisterMigration

* chore: make playlists opt-out and dashboards opt-in

* chore: adjust dashboard test

* chore: disable enable log in test

* chore: address review comments

- do not use pointer config
- add migration registry

* chore: more consistent naming

* chore: fix playlist discovery test

pkg/registry/apis/dashboard/legacy/sql_dashboards.go

@@ -154,12 +154,6 @@ func (a *dashboardSqlAccess) executeQuery(ctx context.Context, helper *legacysql
 		return nil
 	})
 
-	// Use transaction from unified storage if available in the context.
-	// This allows us to run migrations in a transaction which is specifically required for SQLite.
-	if tx == nil {
-		tx = resource.TransactionFromContext(ctx)
-	}
-
 	if tx != nil {
 		return tx.QueryContext(ctx, query, args...)
 	}