Add exception details to QJniObject

During refactoring of QtMultimedia module, some of the code clear exceptions manually and have different behavior if there was/wasn't an exception. With the QJniObject in 6.1 it's not possible to do that because exceptions are cleared internally and a default value is returned, this would be fine for object values where we could check for isValid() after the call, but with primitive values that doesn't work.

For that reason we need to add a way for QJniObject to return the details of the exceptions of the call instead of the result only. This probably would be something similar to std::expected.