Move to newer keyring fork (fixes iOS builds)

[gBasil]

This moves from https://github.com/99designs/keyring to a maintained fork of it, https://github.com/ByteNess/keyring. I contributed support for iOS builds to it, and this PR makes ipatool buildable for iOS.

Resolves #136.

Note that:

1. The GitHub Actions workflows need updating, which I haven't done, because I'm not sure what resources are available on the macOS runners.
   • In addition to building it, you need to give it the right entitlements to run it on a jailbroken device.
2. The Go version in go.mod was bumped. I'm not sure if you want it to stay at 1.23.0.
3. I've been only able to get it build for newer iOS versions (specifically 15.0+, for reasons I've outlined here), but I'm reasonably certain that you could get it to work for older versions.