Utilize source maps

[chrisbreiding]

As part of adding code frames for the improved error experience, we need to do the following:

• Enable source maps (unless the user has explicitly disabled them) in the preprocessor
• Gracefully handle the case where the user has disabled source maps
• For errors with a stack:
  • Translate the stack into source code stack
• For command errors:
  • Capture the stack when a command runs
  • If the command fails, use the source maps to trace the command back to the source spec file
  • Pull out the line from the spec file and one two above and below it to display in the error code frame
• For assertion errors:
  • Same as commands but point to and show the assertion
• For reporter UI:
  • Capture the stack when an it runs
  • Display a button in the UI next to the test name that opens the file at that line when clicked

Related: #881