gather Fibers
For every existing fiber that isn't already captured by another debugger, bind that fiber to this debugger. Those fibers are not permitted to run unless this debugger says they may. Any fibers launched after this point (say, to compute a print representation or evaluate an expression) will not be captured by this debugger.
Must be called from within a safe point, to ensure no fibers are running. It acquires the runtimeLock to prevent conflict with other safe point tasks.
Parameters
fibers Provider
A function producing the collection of fibers to check for capture.