[Concurrency] Task names

[ktoso]

Work in progress on adding names to tasks.

Pending SE proposal.

[mikeash]

Retaining the Swift string makes sense to me. It avoids an extra copy when the string is dynamic, and avoids any copies when it's constant. I'm not sure how inconvenient it would be to manipulate a String from the C++ side of things.

[ktoso]

Yeah, so sadly it's quite painful to make this work... we have to manually inspect flags in the String's flags and then copy or not copy accordingly... I'll try to prepare our ABI so we COULD do this but I will probably not do so in the first impl.

[mikeash]

Is our LTO good enough to have the stdlib expose some minimal calls for us to use here, and have it optimize to something reasonable? (Or maybe this isn't performance sensitive enough for that to matter anyway?) We'd really want to reuse the existing String code and treat it as an opaque value here.

[ktoso]

Build problem nr 1, I can't figure out how to get the gyb generated file included in the module 🤔

[ktoso]

This gyb replaces a few thousand lines (and like 20 definitions) of addTask implementations. We still have ad hoc ones though, and I can't get the gyb result to be included in the build so there's workarounds here still

[ktoso]

@swift-ci please smoke test

[ktoso]

@swift-ci please smoke test

[ktoso]

@swift-ci please smoke test

[ktoso]

The build isn't still right, we still need the stdlib/public/Concurrency/TaskGroup+Embedded.swift workaround file... @etcwilde maybe we can investigate some more -- basically when we checked I had that file still, even while we removed other workarounds so it seemed to work (i.e. see the gyb generated functions), but seems it doesn't still

[ktoso]

@swift-ci please smoke test

[ktoso]

resolves rdar://88918762