certtool: order DN components by scale.

Certtool should default to ordering the components of the DN by scale (least specific to most specific), for both certificates and certificate requests.

Please note discussion in the commit message about "API" for interactive use of certtool. I think I've justified the change, but reasonable people may disagree.

This should resolve #1243 (closed). It is necessary for me to produce the next revision of draft-ietf-lamps-samples.

Checklist

• Commits have Signed-off-by: with name/author being identical to the commit author
• Code modified for feature
• Test suite updated with functionality tests
• Test suite updated with negative tests
• Documentation updated / NEWS entry present (for non-trivial changes)
• CI timeout is 2h or higher (see Settings/CICD/General pipelines/Timeout)

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTION.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code