test1521: verify setting options to NULL better

test1521: verify setting options to NULL better

Previously this test allowed several error values when setting options.
This made this test miss #14629.

Now, errors are generally not accepted for setopts:

 - numerical setopts accept CURLE_BAD_FUNCTION_ARGUMENT for funny input
 - the first setopt to an option accepts CURLE_NOT_BUILT_IN or
   CURLE_UNKNOWN_OPTION for when they are disabled/not built-in
 - there is an allowlist concept for some return code for some variables,
   managed at the top of the mk-lib1521.pl script

In curl.h: remove the OBSOLETE named values from the setopt list.

Closes #14634