use.t: allow multiple whitelist regexps with words and whitespace

There is no reason not to support multiple whitelist regular expressions, and documentation in autopkgtest.pod says we already do.

Also, ignoring whitespace and limiting to just one word are unnecessary and potentially confusing restrictions that can be lifted.

While at it, also allow multiple module names in use-name and improve the diagnostics to list any non-whitelisted output on failure.

Closes: #1008267