Bring more options to the default configuration template

[sanchpet]

Hello! I propose to add some new changes to give users more control over configuration template:

1. Add directives for ca-base and crt-base
2. Allow to define custom default log-format
3. Allow to define custom list of default options, preserving the one that was used in this role as default
4. Make cookie insertion optional
5. Allow to define default-server configuration for backend
6. Add support for prometheus metrics exporter that is built-in in HAProxy now

I have tested this setup with HAProxy version

HAProxy version 2.6.12-1+deb12u3 2025/10/03

Which is installed now by default on Debian 12.

[sanchpet]

@geerlingguy could you please consider reviewing and giving a feedback on this?