Overhaul documentation of makejdk-any-platform.sh

[sxa]

Some thoughts:

• Validate that all options in the documentation are actually usable
• Validate that the options to the script are all documented
• Check for references to the jep319 certs option and remove if it is now completely obsolete (As @M-Davies pointed out, it's still used in various places although Build cacerts during build from Mozilla's list, take 2 #2113 should remove it)
• Consider removing the man page
• If we keep the man page, consider not duplicating it [in README.md])(https://github.com/AdoptOpenJDK/openjdk-build#the-makejdk-any-platformsh-script)
• See whether it can build all the things it claims to (amber for example ... We should probably try using that in [JavaFutures] if it can be made to work easily ...
• Maybe have a "one-option-per-line" option summary from --help instead of the man page.
  Comments welcome :-)