added graveyard tag tests

[shimwell]

Proposed changes

Work in progress. This PR will add the option of exporting the DAGMC file with a graveyard. This is useful for codes that don't yet support implicit graveyards or allow graveyards to be made from CSG cells.

I've added unit tests but need to add the functionality next

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Code refactoring
• Documentation Update (if none of the other choices apply)
• New tests

Checklist

• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[shimwell]

The Unexpected argument '(typing.Any,)' error already has an open PR on Cadquery so looks like this will be fixed soon.

I've tested this with the two neutronics examples on fusion-energy org