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GH-37188: [MATLAB] Move `test/util/featherRoundTrip.m` into a packaged test utility function (#37190)

> **Warning** - Please don't merge this PR. It is still in progress.

### Rationale for this change

To simplify access to the `featherRoundTrip` function that is used in the `tfeather.m` tests this pull request moves the `featherRoundTrip` code into a new packaged test utility function `arrow.internal.test.io.feather.roundtrip`.

This makes it possible to`import` the function, rather than having to manually add the `test/util` folder to the MATLAB Search Path in the test class setup.

### What changes are included in this PR?

1. Moved `test/util/featherRoundTrip.m` code into a new internal packaged test utility function `arrow.internal.test.io.feather.roundtrip`.

### Are these changes tested?

Yes.

1. Updated all `tfeather.m` test cases to use new packaged function `arrow.internal.test.io.feather.roundtrip`.

### Are there any user-facing changes?

No.

This new packaged function is an internal test utility.

### Future Directions

1. Delete the old Feather MEX code.
2. Move more shared test infrastructure into packaged test functions under `arrow.internal.test.*`.
* Closes: #37188

Authored-by: Kevin Gurney <kgurney@mathworks.com>
Signed-off-by: Kevin Gurney <kgurney@mathworks.com>