refactor: from flat layout to src layout

[mdevolde]

refactor: from flat layout to src layout

Why the pull request was made

To respect guidelines concerning packaging in python. The "src layout" is recommended to avoid some problems (during development).

Summary of changes

• Move language_tool_python/ to src/language_tool_python/.
• Patch refs to old language_tool_python/.

Screenshots (if appropriate):

Not applicable.

How has this been tested?

Applied local tests, tested some makefile commands.

Resources

https://packaging.python.org/en/latest/discussions/src-layout-vs-flat-layout/

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (changes to documentation only)
• Refactor / code style update (non-breaking change that improves code structure or readability)
• Tests / CI improvement (adding or updating tests or CI configuration only)
• Other (please describe):

Checklist

• Followed the project's contributing guidelines.
• Updated any relevant tests.
• Updated any relevant documentation.
• Added comments to your code where necessary.
• Formatted your code, run the linters, checked types and tests.