The CI swift workflow needs to be updated to accommodate the macOS
standalone build. This required a decent amount of refactoring to make
the Apple build process more maintainable.
Unfortunately this PR ended up being a giant ball of yarn where pulling
on one thread tended to unravel things elsewhere, since building the
Apple artifacts involve multiple interconnected systems. Combined with
the slow iteration of running in CI, I wasn't able to split this PR into
easier to digest commits, so I've annotated the PR as much as I can to
explain what's changed.
The good news is that Apple release artifacts can now be easily built
from a developer's machine with simply
`scripts/build/macos-standalone.sh`. The only thing needed is the proper
provisioning profiles and signing certs installed.
Since this PR is so big already, I'll save the swift/apple/README.md
updates for another PR.
