CN: Group comamnd line options

[dc-mak]

This commit groups the current CN options to make it clearer which are used for what.

This could also be useful in preparation for switching to using subcommands.

[dc-mak]

@cp526 could you check over this? Not familiar with all of these options.

[dc-mak]

And @rbanerjee20 too.

[rbanerjee20]

For the CN executable spec flags, the grouping of those 3 flags is correct, but I would prefer if the module was named something else, and possibly with a flag suffix since without this it might be confused with existing modules like Executable_spec. E.g. Runtime_checking_flag, Executable_spec_flag (the latter would match the existing naming convention for CN executable spec modules).

[cp526]

Agreed about the flag suffix in the module names.

The flag use_peval is probably specific to CN proof; I don't think the executable-spec tool can produce json (though maybe that would be useful in the future?), so the json flag is also specific to CN proof.

[dc-mak]

Thanks - addressed. Any other comments or good to merge?