Auto merge of #117457 - daxpedda:wasm-nontrapping-fptoint, r=wesleywiser

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 rust-lang/rust#117457 (comment) for more context.

Documentation: rust-lang/reference#1420
Tracking issue: rust-lang/rust#44839

Author: bors