Adjust API Availability for Structured Concurrency Backport

[moritzsternemann]

As the Swift Structured Concurrency backport is now available with the release of Xcode 13.2, I adjusted the API availability guards to enable these features on previous OS versions.

I'll also open a follow-up PR in swift-distributed-tracing.

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[swift-server-bot]

Can one of the admins verify this patch?

[slashmo]

Thanks for your PR, @moritzsternemann! Looks good to me ✅ I'm wondering if we should also add #if compiler(>=5.5.2) && canImport(_Concurrency), because that's how it's currently handled in NIO. CC @ktoso, @fabianfett

[ktoso]

@swift-server-bot test this please

[ktoso]

Yeah the #if also has to be adjusted to what we explain in the adoption guidelines: https://github.com/swift-server/guides/blob/main/docs/concurrency-adoption-guidelines.md#if-guarding-code-using-concurrency

[ktoso]

Our "good friend" jazzy messing up builds again, I'll fix this.

[slashmo]

Our "good friend" jazzy messing up builds again, I'll fix this.
@ktoso

Now that DocC seems to be able to generate static websites as well (swiftlang/swift-docc#56), I think we can ditch Jazzy as soon as possible.

[ktoso]

Very true, to be honest perhaps let's not even waste energy on jazzy anymore.

[ktoso]

@swift-server-bot test this please

[ktoso]

I updated the check: 46faa2a

Would you mind doing the same in the other repo @moritzsternemann ?

[ktoso]

@swift-server-bot add to allowlist