[c++] Centralize some `nanoarrow` helpers

[johnkerl]

Issue and/or context: As tracked on issue #2407 / [sc-51048].

Changes:

Extracting readback of core domain, current domain, and non-empty domain are all currently:

• Done slotwise within libtiledbsoma, templatized;
• For Python: there is a loop over dim names in the pybind11 layer lke this https://github.com/single-cell-data/TileDB-SOMA/blob/b3feada0d1282442d1190f56a43670a32dad97ae/apis/python/src/tiledbsoma/soma_array.cc#L671-L830;
• For R: currently these are using TileDB-R -- which is a dependency we're currently removing -- and I don't want to imitate the above in R

The best option for Python/R interop is:

• Push down loop-over-dim-names to libtiledbsoma
• Make more use of nanoarrow to interface with Python and R

The current PR simply moves some code currently used in libtiledbsoma's unit-test logic to ArrowAdapter, where it can -- and will -- be used for readback of core domain, current domain, and non-empty domain for #2407.

Notes for Reviewer:

This is just a code-move. If all existing unit tests pass, that is success. No new unit tests are introduced here, since no new unit tests are needed.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.49123% with 4 lines in your changes missing coverage. Please review.

Project coverage is 61.15%. Comparing base (0efe51a) to head (800479d). Report is 7 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2994 +/- ## =========================================== - Coverage 89.64% 61.15% -28.50% =========================================== Files 39 94 +55 Lines 4096 12378 +8282 Branches 0 781 +781 =========================================== + Hits 3672 7570 +3898 - Misses 424 4617 +4193 - Partials 0 191 +191 ``` | [Flag](https://app.codecov.io/gh/single-cell-data/TileDB-SOMA/pull/2994/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=single-cell-data) | Coverage Δ | | |---|---|---| | [libtiledbsoma](https://app.codecov.io/gh/single-cell-data/TileDB-SOMA/pull/2994/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=single-cell-data) | `46.99% <96.49%> (?)` | | | [python](https://app.codecov.io/gh/single-cell-data/TileDB-SOMA/pull/2994/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=single-cell-data) | `89.79% <ø> (+0.14%)` | :arrow_up: | 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=single-cell-data#carryforward-flags-in-the-pull-request-comment) to find out more. | [Components](https://app.codecov.io/gh/single-cell-data/TileDB-SOMA/pull/2994/components?src=pr&el=components&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=single-cell-data) | Coverage Δ | | |---|---|---| | [python_api](https://app.codecov.io/gh/single-cell-data/TileDB-SOMA/pull/2994/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=single-cell-data) | `89.79% <ø> (+0.14%)` | :arrow_up: | | [libtiledbsoma](https://app.codecov.io/gh/single-cell-data/TileDB-SOMA/pull/2994/components?src=pr&el=component&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=single-cell-data) | `49.39% <92.10%> (∅)` | |

[johnkerl]

Thanks @nguyenv ! :)