MAINT: Re-enable COO tests after fix

[mtsokol]

Hi @hameerabbasi,

As described in llvm/llvm-project#116012 (comment) this PR re-enables COO tests and makes (temporarily) COO instantiation copy-full.

Addition ops with COO still fail though.

[codspeed-hq]

CodSpeed Performance Report

Merging #814 will degrade performances by 32.16%

_{Comparing enable-coo-tests (e4e4687) with main (c0b2b45)}

Summary

⚡ 2 improvements
❌ 1 regressions
✅ 337 untouched benchmarks

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

Benchmarks breakdown

	Benchmark	main	enable-coo-tests	Change
⚡	test_index_fancy[side=100-rank=1-format='coo']	1.5 ms	1.1 ms	+27.96%
❌	test_index_slice[side=100-rank=2-format='gcxs']	2.4 ms	3.5 ms	-32.16%
⚡	test_elemwise[f=<built-in function gt>-backend='Finch'-side=1000]	62 ms	1.5 ms	×42

[hameerabbasi]

Thanks for the deep dive here, @mtsokol

[hameerabbasi]

Thanks for the deep dive here, @mtsokol!

[hameerabbasi]

Seems like this doesn't fix test_add and test_add_dense_sparse, I just tried removing the xfails and it crapped out.

[mtsokol]

Right, the PR's title is imprecise. It enabled test_coo_3d_format and test_asformat only. test_add is still broken.