Cosmetic changes to cabal-install summarized solver output

[yvan-sraka]

This PR modifies the cabal-install CLI behavior by aiming to enhance the solver output slightly (fixing #4251 by grouping rejected versions by package names). This PR is part of the initiative described in this RFC #8939, and aims to be a discussion about cosmetic changes that could be done to improve summarized solver output (bold text, ANSI colors?), as pointed out by @grayjay.

Checklist:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.
• The documentation has been updated, if necessary.
• Manual QA notes have been included.
• Tests have been added. (Ask for help if you don’t know how to write them! Ask for an exemption if tests are too complex for too little coverage!)

[yvan-sraka]

So here may be the right place to discuss and address #8525, I would play a bit with colors and e.g. post an asciinema recording on which we could iterate :)