sly-db loses context of which stack frame was active when nested debugging

[bollu]

• Say I'm at sly-db debugging some stack trace, and so I focus on the 7th stack frame, hit e to evaluate in the stack frame.
• I then type an unbound variable, which takes me to a sub-handler.
• When I quit this sub-handler with 0: [ABORT] Return to sly-db level 1, the cursor has returned to the original debugging view, but the cursor has now moved to the 1st stack frame.
• The ideal behavior is for sly to remember which stack frame/where the cursor was located in each handler's UI. This way, when a child handler is aborted, the cursor of the parent handler UI can be set to the last cursor location.