Allow to provide default options for acme.sh certificates

Summary:
On Alkane PaaS, all certificates have a similar reload configuration,
ie to call the nginx reload script.

This change introduces for this scenario:

• a new pillar certificates_default_options
• a new Salt module certificates to merge it with certificates_options

Co-authored-by: Sami Baghdadi <samlmrb@outlook.com>

Test Plan:

• unit test provicded for new module
• D4102 for deployment on web-001

Differential Revision: https://devcentral.nasqueron.org/D4103