Vends Realm xcframeworks via SPM to save build time

How to release a new version :

• Download from https://github.com/realm/realm-swift/releases last release artefacts realm-swift-.zip
• It should contain multiple xcode versions of Realm & RealmSwift xcframeworks
• Compress & rename the last 2 versions of these frameworks (ex : "Realm_13_4_1.xcframework.zip", "RealmSwift_13_4_1.xcframework.zip", "Realm_14_0.xcframework.zip", "RealmSwift_14_0.xcframework.zip")
• Run swift package compute-checksum from this repo folder for each of the 4 zips
• In Package.swift :
  • Update realmVersion variable value to new Realm version (ex: "10.34.1")
  • Replace swift version with version from current XCode (found here https://xcodereleases.com/)
  • Replace xcode version & checksums
  • Update iOS/macOS/watchOS/tvOS handled versions if Realm handled versions changed
• Push, tag with the same version number as original repo & upload all 4 zips as assets of the release