gh-104050: Add more type hints to Argument Clinic DSLParser() by erlend-aasland · Pull Request #106343 · python/cpython

Annotate the following method signatures:

- state_dsl_start()
- state_parameter_docstring_start()
- state_parameters_start()

Inverting ignore_line() logic, add type hints (including type guard) to
it, and rename to valid_line().