bug(mac): label OSK keys to match the Mac physical keyboard

[sgschantz]

Describe the bug

The OSK in Keyman for Mac should resemble a Mac keyboard so that users can easily map the keys they are typing to the ones that appear in the OSK. Since 1984, the Mac has always had option keys instead of alt keys, so it would be best to rename them on the OSK.

Other special keys can also be modified to match how they appear on the physical keyboard, such as using all lower case letters, spelling out 'control' rather than abbreviating and using 'return' and 'shift' instead of symbols. There have been slight variations in the keyboard labels since the Mac was first introduced, but they have seen little change in many years.

[sgschantz]

Delaying work on this because this is not as simple as a label update. Changing the labels does not look good unless alignment is correct for each key. Modifier names should be left justified for modifiers on the left of the keyboard and right justified for those on the right.

Because all keys are drawn with the same KeyLabelCell, some other property would need to be introduced to distinguish character keys, and left and right modifier keys from each other, so their alignment can vary. Another possibility would be to not use an NSTextFieldCell. The shared objects don't provide an easy way to render different cells differently.