macOS: Map function keys by their virtual key code, not MacRoman charsHEADdev

When mapping incoming key events to their possible key combinations
for shortcut mapping we use UCKeyTranslate, or its modern Cocoa
equivalent [NSEvent charactersByApplyingModifiers:] (which plumbs
to UCKeyTranslate internally).

When doing so for function keys, we get back characters codes such
as 0x01 / ␁ / Start of Heading when pressing the Home key,
or 0x04 / ␄ / End of Transmission when pressing the End key,
which map to kHomeCharCode and kEndCharCode correspondingly
in the MacRoman character codes table from HIToolBox's Events.h

We used these MacRoman character code mappings to turn kHomeCharCode
into Qt::Key_Home and kEndCharCode into Qt::Key_End.

Surprisingly UCKeyTranslate/charactersByApplyingModifiers does
not return the equivalent function key character codes from the
NSEvent.h header, such as NSEndFunctionKey, even if the original
NSEvent we're processing has this as the NSEvent.characters or
NSEvent.charactersIgnoringModifiers, as reported here:

  https://developer.apple.com/forums/thread/803439

This is a problem because key events with the Control (^) key
also (naturally) map to these character codes when fed through
UCKeyTranslate, which resulted in matching shortcuts for Qt::Key_Home
and Qt::Key_End if the user pressed Control+A or Control+D. Or even
worse, if users had shortcuts registered for Ctrl+A and Home, or
Ctrl+D and End, at the same time, these shortcuts would be
considered ambiguous.

To fix this we now map function keys via the keyboard layout
independent virtual key codes from the same HIToolBox Events.h
header, which ensures we only map real function keys during to
Qt::Keys such as Qt::Key_End.

Note that we still consider the keyboard-layout-mapped character
codes for functions keys coming from NSEvent.h, in case there are
layouts that explicitly map to these.

Fixes: QTBUG-134441
Pick-to: 6.10 6.8
Change-Id: Iac8def7540247665562b438bf4af06b4347d33b0
Reviewed-by: Doris Verria <[email protected]>

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