Issues with and improvements to the format and content of coq-packages.json

[palmskog]

I'm looking at the current version of the JSON format for the archive, and there are some elements that should be easy to improve to provide additional value for consumers of the API:

• include the contents of the dev-repo field in OPAM files to indicate the upstream repo (where more recent versions could possibly be obtained)
• include both the synopsis and the description field in OPAM files - currently only description is included
• separate most recent version in released suite from most recent in extra-dev, otherwise the extra-dev version will always "win" - for example, do

"most_recent": {
  "released": "8.11.0",
  "extra-dev": "dev"
}

• the coq-core-dev repo/suite is not included, but many packages in extra-dev depend on packages there
• possibly, do some cleaning of descriptions and synopses, such as removing trailing white space and newlines
• package dependency information is not included at all - in particular, the Coq version requirements are crucial for automation
• build and install commands for packages could be included as well (useful as hints for automation)

[palmskog]

We should also include the contents of the license field in the JSON file. When SPDX identifiers are more widely adopted, this would allow producing easy statistics on popular licenses for Coq packages.