HPCC-10196  Suggested improvement of for cpan mod installations

A suggestion in improvement of HPCC-Platform/sourcedoc.xml regarding the perl
modules required for the runtime regression suite. The additions include a
description of installing these modules using cpanm and a listed view of the
 modules, prefixed by the full command - sudo cpanm - equivalent to the extent
of instructions for installing the main HPCC dependencies.

Signed-off-by: JamieNoss <james.noss@lexisnexis.com>