Upgrade to Swift 6 compiler (Swift 5 language mode)

[Kyle-Ye]

• Darwin platform
  • Update Xcode 16 and add Swift 6 toolchain support on macOS #80
• Linux platform
  • Bump to Swift 6 compiler for Linux #81
• WASM platform
  • Blocked by upstream release

[Kyle-Ye]

Remove WASM support temporary a while ago. SO close the issue.