Vends Realm xcframeworks via SPM to save build time

Origin: https://github.com/realm/realm-swift/releases

How to release a new version :

• Run ./scripts/update.sh 10.38.3
• Run swift package compute-checksum <path> from this repo folder for each of the 4 zips
• In Package.swift:
  • Update realmVersion variable value to new Realm version (ex: "10.38.3")
  • Replace checksums
• Push, tag with the same version number as original repo
• Run VERSION=v10.44.0 gh release create $VERSION --draft --title "$VERSION" --notes "Updated to $VERSION" --repo tomangistalis/RealmBinaries ./*.xcframework.zip to create the release and upload the frameworks.