Call runtime.LockOSThread() automatically for the Qt main thread

[mappu]

Fixes: #72

[jamalsa]

Shouldn't we call runtime.LockOSThread() in init function on qt/qt6 package like shown here: https://go.dev/wiki/LockOSThread? This way we don't need to have a separate call in three places.

[mappu]

The most important thing is that the goroutine that calls LockOSThread is the same one that calls NewQApplication:

• For most MIQT apps, I expect NewQApplication would be called early in main, and so putting LockOSThread in init as per the wiki would have the same effect.
• But, in some cases it might be possible that NewQApplication is called a long time after init. For example, if some app is mostly a non-Qt app (e.g. a daemon) and only initializes a Qt GUI in response to some later event. In that case, LockOSThread would not match correctly.

So I think it's safer to do it this way. The code in three places is not a maintenance problem, since it's autogenerated, and it exists only in one place in the generator. Although for binary size reasons, maybe it would be nice to have only one.