Introduce pre-commit hooks (ruff + clang-format)

[jonasleitner]

This PR sets up pre-commit for automatic linting and formatting using ruff (python) and clang-format (C++) and applies the hook to the code base. Therefore most of the changes introduced were automatically generated by ruff or clang-format.

Configuration

• The line length for the python code was increased to 100 (previously 84), since I feel that 84 (or the ruff default 88) are often a bit short. This choice also decreased the number of ruff errors requiring manual fixes (see below).
• The rules for ruff are not configured and thus the default set of rules is applied, which might change in future ruff versions.
• The ruff and clang-format versions are pinned in the pre-commit configuration. They can be updated by running pre-commit autoupdate, which should be done every now and then. Note that every version update will probably require a (hopefully smaller!) PR similar to this one to apply the new rules and reformat the code base.
• Formatting and linting in the CI and the stub file generation consistently use the pre-commit hook.

While this PR contains mostly changes introduced by ruff and clang-format, a few commits involved manual changes:

• dd556fd: Setup and configuration of the pre-commit hook and its incorporation in the CI.
• f012cb7: Fixing circular imports introduced by the automatic reordering of python imports.
• a8c067d: Mostly generated by ruff but I adjusted like 1-2 of the unsafe fixes.
• ad95a97: Manually fix the remaining like 160 ruff errors (mostly shebangs in non-executable files).
• e6fec68: I added fmt: skip comments to avoid the reformatting of already nicely formatted equations. Probably I missed some places here...