Sass/add mT to particle

[nilssass]

This PR adds transverse mass as a member function to Particle. Besides the general use case, we need the transverse mass for the new BulkObservables class.

[Hendrik1704]

This looks good in general. One thought that came up is that it might be useful to also implement a filter for mT in the filters for Oscar and Jetscape. If you want to generate only a mT spectrum, then this could save a lot of memory. Maybe it's also useful in other cases.

[nilssass]

Thank you for the comment @Hendrik1704 . I will let you know as soon as the PR is ready for the second review

[nilssass]

@Hendrik1704 this PR is ready for a second review.
I have realized that we have quite some code duplications in Filter.py Therefore I have encapsulated some tests of cutting tuples in the new function

__ensure_tuple_is_valid_else_raise_error(value_tuple, allow_none=False)

Besides that, the warning behavior of some cuts were not consistent in case of lower_cut > upper_cut. This PR solves this issue. Now, all cuts will give a warning and automatically switch the order of the cutting values.

[Hendrik1704]

There are a few typos in some comments and also some copy-paste mistakes.

[Hendrik1704]

Are the new nan outputs of the Particle functions captured in the unit tests?

[nilssass]

Are the new nan outputs of the Particle functions captured in the unit tests?

Yes, I have just added them. Once the tests are complete the PR is ready for the final review

[Hendrik1704]

This looks good now. Thanks!

[nilssass]

Great, thank you for capturing the typos :D