* Refactor coverage file enumeration.
* Relocate sanitize_filename function.
* Support sets when writing JSON files.
* Generalize setting of info_stderr mode.
* Split out coverage path checking.
* Split out collection regex logic.
* Improve sanitize_filename type hints and docs.
* Clean up coverage erase command.
* Fix docs and type hints for initialize_coverage.
* Update type hints on CoverageConfig.
* Split out logic for finding modules.
* Split out arc enumeration.
* Split out powershell coverage enumeration.
* Raise verbosity level of empty coverage warnings.
* Add code coverage target analysis to ansible-test.
This change moves all code for the `ansible-test coverage` command into the `coverage` directory.
Each subcommand is split into a separate file.
Only minor spelling changes were made aside from code relocation.
