fix(studio): uniformize readDatabase and projectDetails connString handling

apps/studio/data/sql/execute-sql-query.ts

@@ -42,6 +42,7 @@ export async function executeSql(
   headersInit?: HeadersInit
 ): Promise<{ result: any }> {
   if (!projectRef) throw new Error('projectRef is required')
+  if (!connectionString) throw new Error('Project connection string is required')
 
   const sqlSize = new Blob([sql]).size
   // [Joshen] I think the limit is around 1MB from testing, but its not exactly 1MB it seems