Add tempest run command

This commit adds a new run command to the unified cli endpoint. The
intent here is for tempest to control it's own run story. This
implements the basic runner and selection functionality to use the
command, however it's not necessarily the end state of the command.
The functionality in this patch is just a starting point to add the
command and the basic functionality needed. It is starting with a
limited feature set with the intent to add additional, more complex
functionality in self contained patches after the command exists.

Co-Authored-by: David Paterson <davpat2112@yahoo.com>
Co-Authored-by: Stephen Lowrie <stephen.lowrie@rackspace.com>

Partially-Implements bp tempest-run-cmd

Depends-On: I09299043e536521d48dbe10632621138e3a366e0
Change-Id: I24588b5c00d005320e8719cf82b5dd95662572cf
diff --git a/setup.cfg b/setup.cfg
index 0bf493c..66a8743 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -42,6 +42,7 @@
     list-plugins = tempest.cmd.list_plugins:TempestListPlugins
     verify-config = tempest.cmd.verify_tempest_config:TempestVerifyConfig
     workspace = tempest.cmd.workspace:TempestWorkspace
+    run = tempest.cmd.run:TempestRun
 oslo.config.opts =
     tempest.config = tempest.config:list_opts