utils: Add function generating regex for DNS name globbing

The intent of this function is to be able to provide a globbing operator
or query filters. One should be able to say, for example, something to
the effect of “gnt-instance shutdown '*.site'”.

Also rename a variable in MatchNameComponent.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>