refactor(framework) Update CLI SSL flags

[danielnugraha]

Issue

Description

Having flag that expects multiple argument is confusing to users.

Related issues/PRs

Proposal

Explanation

Update CLI SSL flag to multiple flags that each expects one argument and update the docs accordingly.

Checklist

• Implement proposed change
• Write tests
• Update documentation
• Make CI checks pass
• Ping maintainers on Slack (channel #contributions)

Any other comments?

[Robert-Steiner]

We also need to update the /doc/source/how-to-run-flower-using-docker.rst and /doc/source/how-to-upgrade-to-flower-next.rst file. The --certificates flag also appears in the translations but I'm not sure if need to change them manually.

[tanertopal]

lgtm