API: Initial finch_backend

[mtsokol]

Initial finch_backend setup.

[github-actions]

Test Results

5 900 tests  +1   5 864 ✅  - 3   5m 18s ⏱️ + 1m 59s
    1 suites ±0      36 💤 +4 
    1 files   ±0       0 ❌ ±0 

Results for commit 0650e70. ± Comparison against base commit 32e6e0b.

This pull request skips 5 and un-skips 1 tests.

sparse.pydata_backend.tests.test_compressed ‑ test_reductions_float16[f4-None-sum-kwargs0]
sparse.pydata_backend.tests.test_compressed ‑ test_reductions_float16[i4-None-sum-kwargs0]
sparse.pydata_backend.tests.test_compressed ‑ test_reductions_float16[i8-None-sum-kwargs0]
sparse.pydata_backend.tests.test_coo ‑ test_reductions_float16[f4-None-sum-kwargs0]
sparse.pydata_backend.tests.test_coo ‑ test_reductions_float16[i4-None-sum-kwargs0]

sparse.pydata_backend.tests.test_compressed ‑ test_reductions_float16[f8-None-sum-kwargs0]

♻️ This comment has been updated with latest results.

[hameerabbasi]

Couple of small comments.

[mtsokol]

@hameerabbasi The PR is ready from my side. It contains initial finch-tensor setup where we can run and test existing Tensor API. In the next steps I will start moving pydata_backend tests to a common tests directory and test against common Array API (once we have it in finch-tensor).

[hameerabbasi]

One minor change and this looks good to go.