A full-screen Modal view should not be movable/sizable

[tig]

As noted by @BDisp in #3342 (comment)_

Toplevel created by the Application.Init shouldn't be moveable, otherwise it will behave badly because it represent all the available space on a terminal.

It should also not be sizable (not currently supported, but will be when #2537 is addressed).

This is not just about Toplevels created by Init. In the Adornments scenario, I do not use Application.Top but run the Scenario using Application.Run (editor). The editor Toplevel is meant to be full screen... and it behaves badly as @BDisp noted.

To fix this, I propose modifying the View move/drag code in Adornment (which will be moved to Border asap) to check for Modal == true && IsFullScreen and ignoring Arrangement if so.

We'll have to figure out what IsFullScreen means. It could be something like if (X == 0 && Y == 0 && Width == Fill && Height == Fill)

[BDisp]

We'll have to figure out what IsFullScreen means. It could be something like if (X == 0 && Y == 0 && Width == Fill && Height == Fill)

Well, that depends if the Parent has or not superview. If it doesn't have then it should be if (X == 0 && Y == 0 && Width == Driver.Cols && Height == Driver.Rows)

[tig]

Wasn't what we thought it was. I had a bug in OnResizeNeeded. PR incoming.