unused-non-trivial-variable: Add user blacklist and whitelist

You can now use CLAZY_UNUSED_NON_TRIVIAL_VARIABLE_WHITELIST to
set a comma separated list of user types which you want to warn on.

Conversly, if you disabled the whitelist via export CLAZY_EXTRA_OPTIONS=unused-non-trivial-variable-no-whitelist
then you'll want a blacklist, that's the env variable CLAZY_UNUSED_NON_TRIVIAL_VARIABLE_BLACKLIST, which also
accepts comma separated list.

BUG: 388979