[CN-exec] Introduce mode for switching between source/output locations

[rbanerjee20]

Add CLI mode exec-c-locs-mode for running the preprocessor with/without linemarkers during the preprocessing step on entry to Fulminate.

Enabling linemarkers (now the default) during the preproc step allows the specification source locations to be reported, which is useful and necessary for the experimental stack ownership mode (see #329) to work.

Meanwhile, disabling linemarkers during this step provides the correct locations in the Fulminate output, and the binary can be run through lldb to step through the instrumented C line-by-line. This is done when exec-c-locs-mode is set.

This mode allows the user to switch between the two.

TODO: Update Bennet if necessary.

[rbanerjee20]

@ZippeyKeys12 could you take a look at this and let me know if any changes need to be made for Bennet?

[ZippeyKeys12]

If you want this option to be available for testing, you'd have to add an option to bin/test.ml

[rbanerjee20]

I thought of doing that (and am happy to). I was wondering if it would work out of the box for Bennet as well. I'll add the flag and you can let me know if Bennet's error messages are looking fixed.