feat(vortex-spatial): add collect scalar function

[HarukiMoriarty]

Summary

• add strict homogeneous ST_Collect overloads for lists of Point, LineString, and Polygon
• return the corresponding native MultiPoint, MultiLineString, or MultiPolygon type
• use shared unary dispatch for constant handling and strict outer-null propagation
• reuse geometry storage on the all-valid path and compact only nullable inner elements
• add focused tests and a dedicated microbenchmark

[codspeed-hq]

Merging this PR will regress 1 benchmark

⚡ 2 improved benchmarks
❌ 1 regressed benchmark
✅ 1956 untouched benchmarks
🆕 5 new benchmarks
⏩ 89 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	cold_misaligned[(64, 256)]	4.4 ms	5.3 ms	-16.88%
⚡	Simulation	decode_varbin[(1000, 2)]	78.5 µs	62.4 µs	+25.82%
⚡	Simulation	compress_fsst[(1000, 64, 8)]	1.2 ms	1 ms	+13.04%
🆕	Simulation	linestrings	N/A	167.1 µs	N/A
🆕	Simulation	nullable_points	N/A	308.8 µs	N/A
🆕	Simulation	points	N/A	165.3 µs	N/A
🆕	Simulation	polygons	N/A	167.7 µs	N/A
🆕	Simulation	envelope_of_collected_points	N/A	489.3 µs	N/A

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing nemo/geo-collect (8153fd8) with develop (ff0a26d)}

Footnotes

1. 89 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩