Add NativePromiseRequest and GenericPromise to Forward.h so we don't have to include NativePromise.h in the header
<rdar://problem/117890980>
Pull request: https://github.com/WebKit/WebKit/pull/19934
Committed 270161@main (418679b35cb0): <https://commits.webkit.org/270161@main> Reviewed commits have been landed. Closing PR #19934 and removing active labels.