feat: distribute precompiled framework

[crleona]

Summary

We want to start distributing Amplitude-Swift as a precompiled package, which means compiling it with BUILD_LIBRARY_FOR_DISTRIBUTION (this enables compatibility with future swift compilers, which is why we still target the oldest supported version on macos-latest) and packaging it as an XCFramework. Most build systems will also want dependencies to conform to this as well.

This PR adds a script to create the xcframework, then add it as an artifact to our releases. Initially, this will only be picked up by Carthage builds. Once I can test with an actual release, I'll add an other option for SPM to just use the precompiled version.

Successful release dry run: https://github.com/amplitude/analytics-connector-ios/actions/runs/11512316382

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: no

[bgiori]

Thanks!