feat: export llvm test utilities under llvm-test feature

[ss2165]

Closes #1673

[ss2165]

I believe all the necessary things are documented, I did check docs builds locally

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.27%. Comparing base (1b94d45) to head (1180460). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1677 +/- ## ========================================== - Coverage 77.79% 77.27% -0.53% ========================================== Files 164 166 +2 Lines 28517 28713 +196 Branches 25429 25625 +196 ========================================== + Hits 22186 22187 +1 - Misses 5116 5311 +195 Partials 1215 1215 ``` | [Flag](https://app.codecov.io/gh/CQCL/hugr/pull/1677/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CQCL) | Coverage Δ | | |---|---|---| | [python](https://app.codecov.io/gh/CQCL/hugr/pull/1677/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CQCL) | `92.42% <ø> (ø)` | | | [rust](https://app.codecov.io/gh/CQCL/hugr/pull/1677/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CQCL) | `75.44% <ø> (-0.58%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=CQCL#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

---

🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests