MAINT: Enable copy-on-write support

[codecov[bot]]

Codecov Report

Patch coverage: 40.74% and no project coverage change.

Comparison is base (5dbb5d9) 99.43% compared to head (7f08514) 99.43%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #640 +/- ## ======================================= Coverage 99.43% 99.43% ======================================= Files 75 75 Lines 15442 15452 +10 Branches 2087 2087 ======================================= + Hits 15354 15364 +10 Misses 63 63 Partials 25 25 ``` | [Impacted Files](https://codecov.io/gh/bashtage/arch/pull/640?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard) | Coverage Δ | | |---|---|---| | [arch/univariate/recursions.pyx](https://codecov.io/gh/bashtage/arch/pull/640?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard#diff-YXJjaC91bml2YXJpYXRlL3JlY3Vyc2lvbnMucHl4) | `89.49% <5.88%> (ø)` | | | [arch/conftest.py](https://codecov.io/gh/bashtage/arch/pull/640?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard#diff-YXJjaC9jb25mdGVzdC5weQ==) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Kevin+Sheppard)

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