Move powertest.py into resmoke as a subcommand. This should be an entirely mechanical move of a single file and its caller in evergreen.

Notes:

• The work from July to move a lot of the powercycle setup code from evergreen.yml to buildscripts/powercycle_operations.py can be left as-is. Evergreen is the only consumer of that code at the moment so it doesn't need to be integrated with resmoke.