Switch project to use pyproject.toml

[hagenw]

This modernizes the Python infrastructure of the project:

• Replace setup.py and setup.cfg by pyproject.toml
• Replace PEP8 checking in pre-commit with flake8 by ruff
• Add checking for common spelling errors with codespell in pre-commit

[codecov[bot]]

Codecov Report

Merging #141 (2d23167) into dev (fe196a8) will not change coverage. The diff coverage is 100.0%.

Files Changed	Coverage Δ
audbackend/core/artifactory.py	100.0% <ø> (ø)
audbackend/core/filesystem.py	100.0% <ø> (ø)
audbackend/core/utils.py	100.0% <ø> (ø)
audbackend/__init__.py	100.0% <100.0%> (ø)
audbackend/core/api.py	100.0% <100.0%> (ø)
audbackend/core/backend.py	100.0% <100.0%> (ø)
audbackend/core/conftest.py	100.0% <100.0%> (ø)
audbackend/core/repository.py	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes

[hagenw]

Tests are failing and I don't know why. Forgot to exclude tests/misc/ folder from pytest.