build: add arm64 iOS simulator NuGet RID

[Marc-André Moreau (mamoreau-devolutions)]

Summary

• add the iossimulator-arm64 NuGet runtime asset for Apple Silicon iOS simulator development
• split iOS device and simulator packaging into ios-arm64 and iossimulator-arm64 frameworks
• remove the old ios-universal package asset that carried the Intel x64 simulator slice

Validation

• NuGet dry-run workflow succeeded: https://github.com/Devolutions/picky-rs/actions/runs/27829764920
• downloaded picky-nupkg from the dry-run workflow and verified runtimes/ios-arm64 plus runtimes/iossimulator-arm64 are present
• verified runtimes/ios-universal, runtimes/ios-x64, and runtimes/iossimulator-x64 are absent from the package