Breakpoints unresolve when adding new breakpoints

[DanTup]

Something odd going on here:

[DanTup]

Fix at https://dart-review.googlesource.com/c/sdk/+/291763.

This may impact Dart-Code integration tests (like it impacted DDS tests) because we can't assume when setBrekapoints() returns that the VM has been updated yet.

[DanTup]

I changed this so we still respond to setBreakpoints after the VM was notified now, but we just delay sending the events back.

[DanTup]

Fixed by dart-lang/sdk@b984c30. Will need a DDS release and rolling into Flutter.