[swift-inspect] Expose task completion flag

[kastiglione]

Depends on #80183.

[kastiglione]

@swift-ci smoke test

[kastiglione]

oh wait, I bet I need more plumbing…

[kastiglione]

yep, I missed swift_reflection_asyncTaskInfo.

From #77167 (review):

We should probably add things to the C interface as well, but that's harder since we don't want to break the ABI. Not sure what the best approach is there, we can add a swift_reflection_asyncTaskInfo2 with the new stuff, but that could grow a lot of variations.

[mikeash]

Adding a new struct and a new function every time we want to add a field is going to be a pain.

I'm thinking, for new C Remote Mirror APIs, we should switch to returning a pointer to a struct instead of a struct. We have allocateTemporaryObject in the wrapper code to make it easy to return a pointer that's valid until the next call. Then we can add fields to existing structs returned in this manner without breaking old clients. We can put a version number at the front of each one so that new clients know which fields are valid and which should be ignored. We'll still need a 2 variant for this call, and any others which we want to evolve, but at least it would stop there.

Alternatively, we could have the caller pass a buffer and a size, and we fill out as much of the struct as will fit. This would be more awkward to call but maybe a bit more efficient.

[kastiglione]

That sounds like a good solution @mikeash.