[MS connector] Edge case: handle garbage collection of folders moved out of non-drive top-level folder

[philipperolet]

We are alerted that a folder moved out of a given top-level folder by incremental sync, but we don't know which one:

• either we have perpetual garbage collection
• or we launch a top-level folder specific garbage collection when that happens

Design TBD

[philipperolet]

codependency with #5751