Replace nested dictionaries with lists

[alessfg]

Proposed changes

Modify servers, servers.listen, server.locations, upstream and upstream.servers from nested dictionaries in the http and stream configuration templates to lists, as well as modify the nginx_config_html_demo_template variable from a nested dictionary to a list. To update your templates, replace the aforementioned nested dictionary keys by lists (place a dash in front of the topmost nested value within each aforementioned nested dictionary).

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• I have added Molecule tests that prove my fix is effective or that my feature works
• I have checked that all Molecule tests pass after adding my changes
• I have updated any relevant documentation (defaults/main/*.yml, README.md and CHANGELOG.md)