Add documentation for the configure_package_config_file() and
write_basic_package_version_file() commands.
Update the comment for the installation of those files to allow a
stopping point for the code display.
Issue: #22663
Extend the change from commit 9e5bbb69ea (Tutorial: Add captions for
code blocks, 2021-06-11) to also add a Sphinx named target to code
blocks. Name each target after the change the code block makes.