moving tests around for better organization

The main drive here is V8 isolation. I noticed that when running both benchmarks in the same process, V8 internal optimizations mess up the results, potentially due to the "delete" statements in "set". Separating them reflects better consistency in the results. Also, in preparation for the new insert-ordered algoritms that I'm working on, it is better to have separation. 

Moving tests/run.js under "unit" to follow our current convention.