ci: GitHub Actions for Xcode 15 beta

[BrandonStalnaker]

Summary

• Updated to add xCode 15 runs for all existing tests

Testing Plan

• Was this tested locally? If not, explain why.
• {explain how this has been tested, and what, if any, additional testing should be done}

Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

• Closes https://go.mparticle.com/work/SQDSDKS-5587

[BrandonStalnaker]

@einsteinx2 Ready for Review. Note: We won't be merging this in until we are ready to update minimum deployment version to iOS 12

[einsteinx2]

closing in favor of #220