build: Use a zip instead of dmg for macOS releases

Implements #18128 (closed) (mostly). From discussion on that issue we've got 3 ACKs (to move from .dmg to .zip), 1 ~0 and 1 NACK. So I've opened this PR to give a better overview of what the changes might actually look like.

Gitian builds currently work, however I haven't tested the signer, and that likely needs some additional changes. As mentioned we can drop quite a few packages from depends. There's some commits here that can cleaned up, squashed or dropped.

If you're compiling macOS, make appbundle will (as before) build a dynamically linked Bitcoin Core.app. make deploy will still build a statically linked dist/Bitcoin Core.app and will now also create a dist/Bitcoin-Core.zip.

Compiling on Linux there has never been a make appbundle rule, and with these changes, make deploy now behaves the same as on macOS. The make deploydir rule has been removed.

Initially I was unconvinced (of a swap from .dmg to .zip), however I have come around after looking at these changes. If there is not agreement that "this is the way", then I'll revive #18151 and fix it up to include xorriso in depends etc.