common.py has queue names that always get overridden by production.py
and lead to confusion.  Set a default SERVICE_VANIANT in common.py and
then set the queue names based on that in common.py so that
production.py doesn't make it more complicated.

This should prevent the issue where if you copy a queue name in
common.py it ends up being incorrect in the production system.  This is
what happened with the sample_task change.

https://github.com/edx/edx-platform/pull/23731 made it so that the queue
name for that queue is independently configurable but the default was
set to the value of HIGH_PRIORITY_QUEUE in common.py which is not the
same as the value set in production.py leading to stale tasks that never
get picked up in production.

BREAKING_CHANGE: If anyone was building a different settings file on top
of common, the default names in common.py are now change to be service
variant specific. eg 'edx.cms.core.high' instead of 'edx.core.high'