Finishes #378
Supercedes #4159
This adds a new enum value for `macos-non-native-fullscreen`:
`padded-notch`. This value will add padding to the top of the window to
account for the notch on applicable devices while still hiding the
menu.
This value is preferred over "visible-menu" by some people because for
screens without a notch, the window will take up the full height.
The plan in the future is that we may color the padded area when a notch
is present. In this commit it appears as transparent.
This changes quit signaling from a boolean return from core app `tick()`
to an apprt action. This simplifies the API and conceptually makes more
sense to me now.
This wasn't done just for that; this change was also needed so that
macOS can quit cleanly while fixing #4540 since we may no longer trigger
menu items. I wanted to split this out into a separate commit/PR because
it adds complexity making the diff harder to read.
First, this commit modifies libghostty to use a single unified action
dispatch system based on a tagged union versus the one-off callback
system that was previously in place. This change simplifies the code on
both the core and consumer sides of the library. Importantly, as we
introduce new actions, we can now maintain ABI compatibility so long as
our union size does not change (something I don't promise yet).
Second, this moves a lot more of the functions call on a surface into
the action system. This affects all apprts and continues the previous
work of introducing a more unified API for optional surface features.
