Sphinx-argparse-cli

- Don't raise label clashing warnings for options which only differ between upper and lower case

- Fix reference clashing for options which only differ between upper and lower case
- Do not render default values for `store_true` and `store_false` actions

- Support Python 3.10

- Support for adding custom subsection group title prefix (`group_title_prefix` and `group_sub_title_prefix` directive
arguments)

- Support for using the `ref` sphinx role to refer to all anchor-able objects generated by the tool
- Flags now have their reference title set (for the HTML builder this is shown when hover over the reference)
- Anchors generated no longer collapse multiple subsequent `-` characters (to avoid clash when there's a flag and a
positional argument with the same name)
- Added a sphinx flag `sphinx_argparse_cli_prefix_document` (by default `False`) to avoid reference clashes when
multiple documents generate the same reference labels
- The root `prog` name now is prefixed for the root level optional/positional arguments' header (to avoid multiple
anchors with the same id when multiple commands are documented in the same document)

- For sub-commands use the parser description first as description and only then fallback to the help message