expand fine_patch documentation to cover both possible levels

[MarcelHoh]

• [✅ ] Small enough (< few 100s of lines), otherwise it should probably be split into smaller PRs
• [✅ ] Tested - See below screenshot of built documentation
• [not relevant ] Runs on GPU (basic: the code compiles and run well with the new module)
• [not relevant ] Contains an automated test (checksum and/or comparison with theory)
• [✅ ] Documented: all elements (classes and their members, functions, namespaces, etc.) are documented
• [not relevant ] Constified (All that can be const is const)
• [✅ ] Code is clean (no unwanted comments, )
• [✅ ] Style and code conventions are respected at the bottom of https://github.com/Hi-PACE/hipace
• [✅ ] Proper label and GitHub project, if applicable

Any comments on the wording are very welcome.

[AlexanderSinn]

Some of the CI tests fail for an unrelated reason; it should be fixed soon.

[AlexanderSinn]

Can you merge development into this branch. That should fix the CI tests

[AlexanderSinn]

Thanks for this PR!