WireGuard Configurations Gone After iOS 15 Upgrade

[Jason A. Donenfeld]

Hey folks,

Small update: I've managed to update a fresh 14 device to 15 using the
latest build, and things are broken still.

On the plus side:
- The new build no longer deletes VPN profiles when the corresponding
keychain references are unresolvable, so if there's any chance of
recovery in a next build, it won't ruin those chances.
- Now that I can reproduce it, I can hammer away at trying to fix this directly.

On the minus side:
- The fact that a keychain reference goes stale during an update from
14 to 15 sounds solidly like an Apple bug, rather than any sort of API
misuse.
- I'm skeptical that there'll be a workaround, and if there is, it
will probably be pretty ugly.

If anyone knows the SecItem APIs well, the file in question is:
https://git.zx2c4.com/wireguard-apple/tree/Sources/Shared/Keychain.swift

So, I guess I'll jump into this in full force now. Here we go...

Jason