docs: update CIPHERS.md

Give a more consice overview of curl's cipher options and cipher suites.

Removed long lists of ciphers that were directly copied from the SSL
backends' documentation. Instead present the user a more common aproach
acorss the SSL backends, with notes for backends that do not conform
and/or provide alternate means.

Provide a shorter list of cipher suites that is more relevant for
modern usage and should work mostly across all backends, a seperate
list with all cipher suites, and a list of links to the SSL backends'
documentation for more information.

Also give examples with modern cipher suites.