wasm: Take advantage of Wasm 2.0 features

[johanbrandhorst]

The WebAssembly Working Group of the World Wide Web Consortium (W3C) published a first draft of release 2.0 of the WebAssembly spec: https://webassembly.github.io/spec/core/. The new release contains some new features, some of which may be interesting to the Wasm architecture backend of the Go compiler. There is a summary of the new features available in the Change History section: https://webassembly.github.io/spec/core/appendix/changes.html#release-2-0.

I'm opening this issue to foster a discussion on what, if any, new features may be interesting to take advantage of and when, if ever, the Go Wasm backend should use these newer features.

[ianlancetaylor]

CC @neelance

[beoran]

Function types allow more than one result

This seems like something Go could use immediately to optimize funcs with multiple return values.

[neelance]

Let's not open a new discussion here. This belongs to the existing discussion at #28360.