This updates the `showUserPrompt` method to accept a cancellation token so that if requests are cancelled (by the client, or something like a second refactor cancelling the first), the prompt is also cancelled (and when the response arrives, it can be ignored).
Note: Unfortunately the protocol (and VS Code) don't actually allow for the prompt to be cancelled/hidden from the user, this is mainly to avoid us keeping the request "alive" on the server if the user ignores a prompt and we know the parent request was cancelled anyway.
Fixes https://github.com/dart-lang/sdk/issues/63285
Change-Id: Ia77880a749b284a2ff31c8cf560307ad908d2175
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/499360
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Danny Tuppeny
c5fb640747