Stabilize Wasm target features that are in phase 4 and 5 This stabilizes the Wasm target features that are known to be working and in [phase 4 and 5](https://github.com/WebAssembly/proposals/tree/04fa8c810e1dc99ab399e41052a6e427ee988180). Feature stabilized: - [Non-trapping float-to-int conversions](https://github.com/WebAssembly/nontrapping-float-to-int-conversions) - [Import/Export of Mutable Globals](https://github.com/WebAssembly/mutable-global) - [Sign-extension operators](https://github.com/WebAssembly/sign-extension-ops) - [Bulk memory operations](https://github.com/WebAssembly/bulk-memory-operations) - [Extended Constant Expressions](https://github.com/WebAssembly/extended-const) Features not stabilized: - [Multi-value](https://github.com/WebAssembly/multi-value): requires rebuilding `std` #73755. - [Reference Types](https://github.com/WebAssembly/reference-types): no point stabilizing without #103516. - [Threads](https://github.com/webassembly/threads): requires rebuilding `std` #77839. - [Relaxed SIMD](https://github.com/WebAssembly/relaxed-simd): separate PR #117468. - [Multi Memory](https://github.com/WebAssembly/multi-memory): not implemented. See https://github.com/rust-lang/rust/pull/117457#issuecomment-1787648070 for more context. Documentation: https://github.com/rust-lang/reference/pull/1420 Tracking issue: https://github.com/rust-lang/rust/issues/44839