Opt out of process tree compacting

[int19h]

See microsoft/vscode#99736 for details on process tree compacting. Note that this is already in VSCode Insiders.

TL;DR is that when there are multiple debug sessions in a parent/child chain where each session has exactly one child (except for the last one that has none), VSCode is going to start combining them into a single logical session item in the Call Stack window. That item has title coming from the root session, but all debug controls are applied to the child session. Furthermore, the hovering debug toolbar also reflects the child session.

This is a problem wrt Stop/Disconnect in particular, because in Python multiproc, all child sessions are "attach" (even if the root was "launch"), and thus would show Disconnect rather than Stop. The floating toolbar thus also shows Disconnect. And having a parent session with a single child is the most common multiproc scenario for us, because that's exactly what Django and Flask do with auto-reloading enabled.

(Before this VSCode change, the floating toolbar would correspond to the current selection in Call Stack - if parent session is selected, then it'd show Stop. In addition, since sessions would each have a separate item in Call Stack, each item would have its own inline mini-toolbar there.)

There's a feature request on VSCode to provide the ability for the extension to specify which session should be "in charge" of Stop/Disconnect: microsoft/vscode#101140. However, until that feature is implemented, we should opt out from compacting, so that web app debugging experience does not regress for our users.

[int19h]

How to opt out:
microsoft/vscode#100852

[int19h]

No longer needed.