update sys_vars.innodb_compression_algorithm_basic to pass

it checked that the default is lz4. Which only worked on systems that
had lz4 and did not have lzo. Now it checks for the default to be zlib,
which works on systems that has neither lz4 or lzo. Like our package
builders in buildbot. This is intentional, we don't want introduce
additional dependencies (lz4, lzo) for our packages just yet.
This can (and will) be reconsidered, and this test can (and will)
be updated again.
MDEV-6137 better help for SET/ENUM sysvars

Auto-generate the allowed list of values for enum/set/flagset options
in --help output. But don't do that when the help text already has them.

Also, remove lists of values from help strings of various options, where
they were simply listed without any additional information.