doc: Convert UUID functions list to table format.

doc: Convert UUID functions list to table format.

Convert the list of UUID functions into a table for better
readability. This commit also adds references to the UUID type section
and includes descriptions of different UUID generation algorithm
versions.

Author: Andy Alsup <bluesbreaker@gmail.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Discussion: https://postgr.es/m/CADOZ7s7OHag+r6w+BzKw2xgb3fVtAD-pU=_N9-9pSe5W1TB+xQ@mail.gmail.com