Extension for Ansible redirects

[oraNod]

Fixes #2147 and supercedes #2266

This PR extends the Sphinx reredirects extension to load redirects for Ansible documentation from a toml file. The purpose is to replace the httpd mod_rewrite rules in https://github.com/ansible/docsite/blob/main/ansible/11/.htaccess and https://github.com/ansible/docsite/blob/main/.htaccess in a way that is compatible with ReadTheDocs.

If this PR is accepted and merged, there are two follow on actions:

• Create a robots.txt file to stop crawlers from indexing the generated HTML files. We can put the robots.txt file in the ansible/docsite repo and copy it across as part of the ReadTheDocs build.
• Remove all the existing stub files from this repository. For example, all the files under the docs/docsite/rst/user_guide folder.

[samccann]

LGTM

[oraNod]

@webknjaz / @felixfontein / @gotmax23 Could we please get another round of reviews here? I've added all the redirects to the ReadTheDocs project and this PR is one of the last hurdles in the way of the docs.ansible.com migration. Thanks.

[oraNod]

@webknjaz Hey again, thanks for the previous comment that made me re-think this. What I had here before was garbage. I'm not sure how it got muddled up so my apologies.

When the generate-redirects input is true, the command is make webdocs EXTRA_TAGS="-t redirects" ANSIBLE_VERSION=""

When generate-redirects is false, the command is make webdocs ANSIBLE_VERSION="". It does look like there's an extra space between webdocs and ANSIBLE_VERSION but I don't think that has any effect in how the make command gets evaluated.