Test that we can override variables set in inventory when the vars_file name is templated

Fixes #8903
Prevents module from failing with "_mysql_exceptions.Warning: Sending passwords in plain text without SSL/TLS is extremely insecure." When not using SSL/TLS.
Merge pull request #8953 from jsmartin/mysql_fix

Prevents mysql_replication from failing with "_mysql_exceptions.Warning: Sending pa...
Add documentation about bin_ansible_callbacks setting.  Standardization and cleanup.
Add version_added info.
Modules are almost always written now by mutliple authors, so don't show this field on website, since it grows obsolete and does not take into account all contributors.
Contributors are still listed on github module source and in repo, and original authors still in the file for when development questions arise, but want
to funnel support questions to the mailing list versus directly to them.
Fix typo in redis cache change from 10afaee1