Better debugging in WebAssembly

[tidoust]

This includes:

• Ability to instrument large codebases with DWARF
• Ability to give workers a meaningful name after creation
• Ability to stop main UI thread and all workers at once

Raised in:

• A Non-linear Video Editor built with WebAssembly

[junyuecao]

https://developer.mozilla.org/en-US/docs/Web/API/Worker/Worker Currently a worker's name can not be modified after creation. That makes all the thread names are the same or only with a worker number (https://github.com/emscripten-core/emscripten/pull/13999).

[connorjclark]

FYI https://github.com/whatwg/html/issues/7838