Run by line: Continue on the line we left off after fixing an error, instead of at the top

[bamurtaugh]

Testing microsoft/vscode#133903

• RBL through a cell
• Error in cell, i.e. ModuleNotFoundError: No module named 'pydotplus'
• RBL stops and line is no longer highlighted
• Once I fix the error (i.e. install missing module), if I start RBL in cell again, have to restart from top
• Could it make sense to:
  • Keep error line highlighted? At first when I ran into errors (i.e. some imports missing early on in a cell), I thought perhaps RBL stopped when it encountered from statements
  • Keep user's place? So that when I install the package and RBL again, I can pick up where I left off?

I'm not sure if this makes sense or would be feasible since an error stops the cell from running, but wanted to share my initial thoughts as I ran into errors while running by line.

[DavidKutu]

Cool idea, Thanks

[roblourens]

This is essentially #5621, not straightforward