Exp: Add RTree index for polygon

[ringsaturn]

• Please note that this PR is still WIP.
• Memory usage increase a lot for tzf-ts use case(from 40MB to 140MB), which should be fixed.
• For timezone query in tzf-rs's Finder use case, a benchmark runs on world cities on my MacBook Pro:
  • Previous version could run 70 Kops/s
  • This version could run 170 Kops/s
• tzfpy perf diff:

  Name (time in us)               Min      Max    Mean  StdDev  Median     IQR  Outliers  OPS (Kops/s)  Rounds  Iterations
  ------------------------------------------------------------------------------------------------------------------------
  -test_tzfpy_random_cities     2.5024  26.9442  5.7295  2.7556  5.1883  3.3751  6551;618      174.5363   20000          10
  +test_tzfpy_random_cities     2.4133  14.5704  3.8425  0.9685  3.6863  1.2162  6779;364      260.2482   20000          10
  ------------------------------------------------------------------------------------------------------------------------

• US AZ benchmark

  -test benches_az_polygon::poly_contain_point     ... bench:       2,704 ns/iter (+/- 18)
  -test benches_az_polygon::poly_not_contain_point ... bench:       2,715 ns/iter (+/- 5)
  +test benches_az_polygon::poly_contain_point     ... bench:         189 ns/iter (+/- 2)
  +test benches_az_polygon::poly_not_contain_point ... bench:          90 ns/iter (+/- 2)

• Refer Speed up look up #3

---

TODO:

• Reduce memory, RTree cost lot. Move to Reduce RTree index memory usage #6
• Add option to set whether index is need: for most case RTree index is not need.
• Append a real world benchmark for point-in-polygon check: another PR will do this. Add benchmark on US AZ #5