Add executable to write CCE worldtube coords to a file

[knelli2]

Proposed changes

Part of #6246. A C++ executable was explicitly chosen for this even though it is very simple so it can be compiled and distributed like our other CCE executables. A python version would have to have some kind of PyBindings packaged in and that didn't seem like the best approach.

I added a function that does this, bound it in python just in case we want to use it, and then made the executable.

I currently don't add this to the tarball that we create at each release because there is still work that needs to be done in the CCE executable and the ReduceCceWorldtube executable. Once that is done, then I will add this executable.

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[nilsdeppe]

Thank you for doing this! LGTM, just a couple small suggestions. Please squash right away :)

[nilsdeppe]

[optional] name this overwrite_file to be explicit?

[knelli2]

@nilsdeppe Squashed, thanks!