agent0: bring back smart_long policy

[dpaiton]

We deleted the smart_long.py and smart_short.py files in #909 because it required a few yieldspace functions and the variable rate, which we no longer support. Once #910 and #913 are complete, we should be able to bring both back.

[dpaiton]

smart long: https://github.com/delvtech/elf-simulations/pull/994/files

Not bringing back smart_short because it wasn't very smart.