Dart 3.14 adds SDK migrations, faster Wasm and DartPad

Dart 3.14 introduces dart migrate, a tool that prepares code, updates package SDK constraints, and can apply optional cleanup fixes across one or more SDK versions.

The release also adds hardware 128-bit WebAssembly SIMD support, reporting up to 4x speedups in native and WebAssembly SIMD benchmarks, while standalone Wasm output can run without a JavaScript host.

A re-engineered DartPad beta now runs Dart tooling locally in the browser, with LSP features, pub.dev package access, and multiple-file support.