QKeySequenceEdit: make it configurable how to end the recording

As a user,

I would like to be able to terminate the shortcut recording by enter / carrier return rather than a time,

so that I can end the recording session immediately rather than waiting for timeout.

One slight drawback, of course, is that this key would not be used for the actual shortcut itself, but this is a decision that the application developer needs to make, weighing pros and cons in the application context, rather than the framework.

A new opt-in API would be helpful for this, something like:
QKeySequenceEdit::setFinishKey(Qt::Key_Return);