perf: improvements to area processing

[aoles]

Summary of changes

• Pre-check against bounding boxes first before performing a full geometrical check
  • 2x speedup of area mapping (132 s vs. 281 s)
  • 12% speedup of second pass (520 s vs. 593 s)
• Reduce grid size from 1.0 to 0.5 degree
  • ca. 2x speedup of 2nd pass (250 vs. 520 s) at a cost of over 3x longer area mapping (448 s vs 132 s)

TODOs

• [ ] parametrized instead of hard-coded grid size
• [ ] for area mapping consider only the sub-grid confined to area's bounding box instead of performing a full grid scan