Make 'working screenrect' to return the safe area on iOS

[livecodepanos]

No description provided.

[livecodepanos]

WIP because this results in black screen, even though the correct safe area is reported:

[livecodepanos]

Note that the safe area is actually the screen rect excluding the area of the top notch and the bottom area of the soft "home" button:

[livecodepanos]

I believe the "black screen" problem is caused because the value of the member variable workarea (of struct MCDisplay) is used in other places in the engine as well, so these places do not like the workarea having the value of the safe area. Or because bool MCScreenDC::platform_getdisplays(bool p_effective, MCDisplay *&r_displays, uint32_t &r_count) is used in several other places apart from MCInterfaceGetScreenRect, and again, these places probably do not like the new value of r_displays[0] -> workarea which is now the safe area.

[livecodepanos]

I have pushed some changes that fix the black screen issue. The working screenrect now reports the safe area, at any point it is called (i.e. either on preopenstack or later after the opencard is sent.