Move System::jsonExit to BaseModule->jsonExit

- This will ensure headers set in BaseModule->run will be carried in jsonExit scenarios
- Deprecate jsonExit() method in Core\System

src/Module/AccountManagementControlDocument.php

@@ -79,6 +79,6 @@ class AccountManagementControlDocument extends BaseModule
 			],
 		];
 
-		System::jsonExit($output);
+		$this->jsonExit($output);
 	}
 }