Lock contention when running the same test multiple times with `pav run`

[hwikle-lanl]

Launching the same test multiple times in quick succession under pav run causes lock contention.

[Paul-Ferrell]

I have a solution for this, but it's a doozy.
I want to get rid of the per-config area tagging of tests and instead make test numbering relative to their series. Tests would still be created based on where they're defined, but numbered relative to the series. We can still lock around series numbers, or do random word names or something.