Use filter name enum for filter lookup/registration

> As the filter names in the XML are quite cryptic and arbitrary at times, it might be a good idea to add an Enum or something that has all the filters that exist. Each member could have a short, but ideally still readable name, and map to the internal XML name. Then each docstring could have the full name shown in the GUI.

I added the [`_enum.py`](https://github.com/DSD-DBS/py-capellambse/pull/84/commits/53d5ff8d92f4e94dc41443c4b7d119cfaadc4c7d#diff-53b1e80fa82574ef23290a955df05ed180a46b18d6768c220b3ee1a59256a7b1R13) where all found filters are stored. Let's finalize this PR by using the filter names defined there. What do you think @Wuestengecko?

_Originally posted by @ewuerger in https://github.com/DSD-DBS/py-capellambse/issues/84#issuecomment-1146777260_