Fix improperly exclusive radio buttons

[Pokechu22]

QRadioButton has an autoExclusive function, but it only works if the buttons share the same parent widget. QButtonGroup can be used to manually specify groups.

Example of the problem

Open the breakpoints tab by selecting View → Breakpoints (the debugging UI may need to be enabled). Then, while a game is running, select "New". Then, click on the "Memory breakpoint" button 4 times. Weird stuff happens.

I'm not 100% sure that this doesn't leak memory; the documentation isn't explicit about what owns the QButtonGroup object (to my understanding, Qt normally manages deletion of objects, but I don't know if it'll follow the addButton chain backwards). We already use it this way in CheatSearchFactoryWidget.cpp though.

[JosJuice]

I'm not 100% sure that this doesn't leak memory; the documentation isn't explicit about what owns the QButtonGroup object (to my understanding, Qt normally manages deletion of objects, but I don't know if it'll follow the addButton chain backwards). We already use it this way in CheatSearchFactoryWidget.cpp though.

Absent any explicit documentation, I would assume it works the way QObjects work in general: They're deleted when the parent is deleted. So I would suggest setting a parent for them.

[Dentomologist]

LGTM, no blocking issues.

• [Nitpicky] The QButtonGroup pointers could be auto* const.

[Pokechu22]

Very little of the existing DolphinQt code uses auto* const, so I'm not going to worry about that for now.