Split function_space_impls.py into smaller files

The file function_space_impls.py has reached a length of 1053 lines. Adding support for additional Finite Element spaces will make it grow further.

The primary purpose of this MR is to split it up into several files:

• one for the abstract base class FunctionSpaceImpl
• one for each Finite Element space (here we combine scalar and vectorial Langrage spaces into one file, e.g. p2_space_impl.py)
• one file for the factory function create_impl() which becomes a free-function instead of a static class method to avoid problems with cyclic dependencies

The files are collected inside their own folder function_space_implementations inside operator_generation.

The secondary purpose is to adapt the code in OperatorGenerationTest.hpp to a name change in HyTeG, see hyteg!849 (merged) and hyteg!851 (merged).

requested review from @he66coqe

added 1 commit

• 584e63ab - Updates OperatorGenerationTest to new function names in HyTeG

Compare with previous version

marked this merge request as ready

added refactoring label

approved this merge request

added 1 commit

• f906be25 - Fixes filenames in __init__.py and updates docstrings in base class

Compare with previous version

resolved all threads

enabled an automatic merge when the pipeline for f906be25 succeeds

merged

mentioned in commit c3815303

mentioned in commit 247429d5

mentioned in merge request !44 (merged)