Modify Qt: Register Installation selection window pop up timing

Assuming no Qt installation is yet register.

Assuming VS code is open without a project, the qt-core extension is not activated.

VS code recommendation window for Qt installation appears when Qt: Register Installation is called. The recommendation appears in the back ground, behind the Qt: Register Installation selection window, making it difficult to focus on the recommandation.

In such a case, it would be nice to have the recommendation window pop up first. If the "Set Qt Installation Root" button of the recommendation window is clicked, the Qt: Register Installation selection window should not open. If the recommendation window is closed or "Do not show again" button is clicked, the Qt: Register Installation selection window opens.