ENH: Add sparse_vector constructor

[mtsokol]

Hi @hameerabbasi,

I started porting Array API vecdot function to Finch MLIR backend. So far it's 1D only so here's a SparseVector format that is needed for it.

[hameerabbasi]

Thanks, I'm working on a more defined way of putting together levels and ops in a lazy fashion.

[codspeed-hq]

CodSpeed Performance Report

Merging #791 will degrade performances by 52.34%

_{Comparing sparse-vector-format (7314e1e) with main (9067817)}

Summary

❌ 1 regressions
✅ 339 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	sparse-vector-format	Change
❌	test_index_fancy[side=100-rank=1-format='coo']	675.5 µs	1,417.2 µs	-52.34%