fix task reconnection

[meganrogge]

fixes #186749 fixes #186373

very similar issue to the one where the build task wasn't discovered -- if the task that's getting reconnected to belongs to an execution which has not yet been registered, then the reconnection will fail and you'll see both of these error messages.

The first message occurs when _jsonTasksSupported is false, which is this case when one or both of these hasn't yet been set.

https://github.com/microsoft/vscode/blob/0e5c0111e868d4b270273f850c36ee334d690468/src/vs/workbench/contrib/tasks/browser/abstractTaskService.ts#L2264-L2266

The second is a byproduct of that since the call to activate that provider doesn't happen

We have a new event which waits for all supported executions or times out.

What we could do is store a variable on before reload which dictates which executions need to be supported for the reconnection to happen. but maybe that's overkill