Add test/values/trap-in-post-return.wast

[lukewagner]

This PR adds a .wast calling all the canon function that contain a may_leave trap from under a post-return function testing that they trap.

[dicej]

That's a big file! Thanks for adding it.

Alex and I are deep in the process of upstreaming wasip3-prototyping into the main wasmtime repo, so I might not have a chance to get this test passing this week, but it's on my to-do list.

[dicej]

FYI, I've got the test passing in this branch, but I'm going to hold off PRing that until we're done upstreaming async support to Wasmtime. We'll probably add a config option to get the old behavior (i.e. allowing import calls in post-return functions) in case this breaks real-world pre-async code.

[lukewagner]

Awesome, thanks!