power up certbot to be able to issue certificates to multiple domains with dry-run capabilities

[ignatius-n]

Description

Fixes:
#2729 (comment)
#2889

Motivation and Context

these changes enable fix several errors including:

1. nginx acme Type: unauthorized error: this was usually due to missing - ./certbot/letsencrypt/:/var/www/letsencrypt volume mapping on nginx service which is now fixed
2. feature to test ssl certificate issuance: with the update you can now test certbot without the risk of hitting the all precious low production rate-limiting that will bur you from requesting additional certificates for at least 1 week.
3. ability to request multi-domain certificates: it was a challenge requesting ssl certificates for multiple domains at once eg abc.com,xyz.info,fake.com at the same time. Right now you can easily achieve this by comma separating all your desired domains and certificates will be generated for each one of them

Changes Made

• Bug fix (Secure Nginx with Let's Encrypt Guide #2889 and CertBot No such file or directory #2679) that was arising during coping of generated certificates. It looked something like
  certbot_1 | cp: cannot stat '/etc/letsencrypt/archive/app.test/cert1.pem': No such file or directory
• New feature (ability to run certbot in test mode i.e dry-run).
• New feature (ability to request ssl certificates for multiple domains at the same time).
• Breaking change (there is a tiny change on where and how certificates are stored). Initially it was like for instance in /var/certs/"$CN"-cert1.pem but now its /var/certs/$CN/cert.pem

Definition of Done Checklist:

• I've read the Contribution Guide.
• I've updated the documentation. (refer to this for how to do so).
• I enjoyed my time contributing and making developer's life easier :)

[johnny-silverhand]

@ignatius-n thank you, is this already usable?