Fix package not building for WASI

[MaxDesiatov]

This package currently doesn't build for WASI, as it refers to platform-specific types like URLSession, URLRequest, and URLResponse types not guarded by OS checks. With these new checks the package builds for wasm32-unknown-wasi triple successfully.

[guoye-zhang]

@swift-ci test

[guoye-zhang]

Can we make HTTPTypesFoundation module completely unavailable on WASI?

[MaxDesiatov]

Even though URLSession is not available on WASI, HTTPRequest is. One would be able to pass that type to some other HTTP client that's not URLSession. Hence there's still value in keeping that extension on HTTPRequest available.

Additionally, there's no clean way to exclude a single platform from a given package graph in SwiftPM. Until something like apple/swift-package-manager#7084 is merged, we can't reliably enumerate all platforms and exclude WASI from that list. You'd have to update Package.swift every time a new supported platform is added to SwiftPM.

[MaxDesiatov]

@guoye-zhang would it be possible to tag a new patch release with this change? Thank you!

[guoye-zhang]

Sure, just waiting for one more change

[MaxDesiatov]

Thank you, much appreciated!