Breakpoints disappear after hot restart

[kenzieschmoll]

In this .gif, you can see we have one breakpoint before hot restarting. Then we hot restart, and the breakpoint disappears. The test application is running on an iOS simulator.

(the gif is a bit misleading since when it loops back to the beginning, it looks like the breakpoint comes back, but that is just the gif starting over)

This is a good candidate for an integration test where we can use a real application and trigger a real hot restart.

[elliette]

This might be related to #3359. I thought this was limited to macos, but it seems to be more widespread. Breakpoints don't disappear when connected to a web app, which makes me think this might be an issue with the vm_service.

[elliette]

Opened dart-lang/sdk#52794 to track the work required for the VM service. Once that's resolved, I will add an integration test. FYI @bkonyi @derekxu16