Fix DynamicRayRunner performance issues. Warmup more works in benchmarking script.

[xcharleslin]

DynamicRayRunner is now similar or faster than RayRunner on all questions of TPCH.

Benchmarking changes:

• Add support for Ray's profiler in TPCH benchmarks. To use, set RAY_PROFILING=1. Official docs here.
• Warm up more workers: one worker per CPU. Currently, we warm up one per node.

DynamicRayRunner changes:

• Correctly track task parallelism. Before, we were overcounting tasks and letting CPUs idle.
• Add spread strategy for reduce tasks.
• Add logger statements and profiling wrapper.

TODO: refactor for cleanliness

[xcharleslin]

Main branch DynamicRayRunner:

Q1: 3.4603s     +1.94% vs RayRunner
Q2: 2.613255s  -40.59% vs RayRunner
Q3: 3.399833s  +40.57% vs RayRunner
Q4: 4.338846s   +5.49% vs RayRunner
Q5: 6.704545s  +58.23% vs RayRunner
Q6: 0.646179s   -2.78% vs RayRunner
Q7: 3.411119s  +31.45% vs RayRunner
Q8: 5.630377s  +41.63% vs RayRunner
Q9: 9.025225s  +54.58% vs RayRunner
Q10: 3.034456s +24.08% vs RayRunner

Total: 42s (+24% vs RayRunner, 34s)

This branch DynamicRayRunner:

Q1: 3.543052s    +4.38% vs RayRunner
Q2: 1.247474s   -71.64% vs RayRunner
Q3: 2.248951s    -7.01% vs RayRunner
Q4: 3.777719s    -8.15% vs RayRunner
Q5: 4.163764s    -1.73% vs RayRunner
Q6: 0.623651s    -6.17% vs RayRunner
Q7: 2.457648s    -5.29% vs RayRunner
Q8: 4.081357s    +2.67% vs RayRunner
Q9: 5.232197s   -10.38% vs RayRunner
Q10: 2.200268s  -10.03% vs RayRunner

Total: 30s (-13% vs RayRunner, 34s)