Add an option that automatically sets a breakpoint at the end of a test

[mdmintz]

Add an option that automatically sets a breakpoint at the end of a test.

• This can be helpful for debugging.
• This can be faster than manually setting a breakpoint at the end of a test before running it.

Currently, there are some similar options, but those are different:

• --pdb (If a test fails, then set a breakpoint at the point of failure.)
• --trace (Set a breakpoint immediately after a test starts.)

Adding an option such as --final-debug could cover the gaps.