get_maintainer: add --bug option to print bug reporting info

For example Documentation/adming-guide/bug-hunting.rst suggest using
get_maintainer.pl to get a list of maintainers and mailing lists to
report bugs to, while a number of subsystems and drivers explicitly use
the "B:" MAINTAINERS entry to direct bug reports at issue trackers
instead of mailing lists and people.

Add the --bug option to get_maintainer.pl to print the bug reporting
URIs, if any.

Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240815113450.3397499-1-jani.nikula@intel.com