[Driver] Improve unused-argument diagnostic for extra sanitizer features.

Don't print unused-argument warning for sanitizer-specific feature flag
if this sanitizer was eanbled, and later disabled in the command line.
For example, now:
  clang -fsanitize=address -fsanitize-coverage=bb -fno-sanitize=address a.cc
doesn't print warning, but
  clang -fsanitize-coverage=bb
does. Same holds for -fsanitize-address-field-padding= and
-fsanitize-memory-track-origins= flags.

Fixes PR23604.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237870 91177308-0d34-0410-b5e6-96231b3b80d8