* fix properly path parsing with nested subdirectories
* fix regex to be able to handle `file://..`
* fix not checking all expected diagnostics
* Some extra comments and renames
- lsp.py: Fixes invalid-syntax by Python interpreter on Windows CI (older Python version).
- lsp.py: Savely strip CRLF from right side of the string, ignoring accidental multiple occurrences of \r (such as \r\r\n).
- lsp.py: Fixes reading single character from stdin (wrt. Windows platform).
- lsp.py: Adds header line reading to I/O tracing (useful for debugging).
- lsp.py: When running the tests on Windows, don't care test file content's newlines but simply expect LFs (instead of CRLF for example).
- Apply pylint notes.
- Fixing use of @functools.lru_cache for older python versions (CircleCI Windows)
