Replace CppUnit with GoogleTest in AX tests

[tstraubinger]

This is a work-in-progress pull request. I've begun by adding GoogleTest to the AX unit test runner and am currently running both the existing CppUnit test suite as well as any added GoogleTest tests. The intention is to migrate the test cases one-by-one and then remove CppUnit completely afterwards.

Resolves https://github.com/AcademySoftwareFoundation/openvdb/issues/1917

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• :white_check_mark: login: tstraubinger / name: Tim Straubinger (5beb2c5367213164af7834184e23eda4a6f2156c, 40a3ef4c058880513c1668031fa38233a3df91e5, 26ada31fa1388b0725ea98a0ce2f8003ab2f6431, 9bb34dff3fd7eff6b020f98e91325117b034997a, 7aa4136886f3141a56f7bc96ffc9dafe9890baf8, 748ace48cd678a904d93f9157cb7ee2d3c35527e, 5c2f8e80f9bc1d81761f352c9ba71120786c371a, efa51761373eef94964b7d31789a59184188e07f, 29a17e36bc633617a7ce966d0abe221cbab18c36, a065b5e3ded37efdf8cdbf8516f5253bcda993ea, b44248b2005e5ee80d3fe3a7dde7576496d66ea9, 18c2c3a99230ec5c3adf838b434242ab4ddd7b96, 3ed5f6e93d634d7b87f972d99b24268b9e366855, 8a13cb2b020eb59120b02b47eda3c10b2680347b, 5df88718270d9048f074dc7d844cd8e9c4b68cd2, f25319edbb8d59262ef0a5c5f048390d67e5329c, 109c3f2591f9c8db416b1410720851b91cc6e8d8, ac56c2496d5b08aceae4c99641fda22002ad724e, dcd67444244ee4fc027d75833f6230e4b7920e8e, 5e6a0d260b14d5d130b9c97ba8214ceb91ea57c7, 68d97534371a5e1f070e6546f054bfccd0a27a66, 692d63e3b8ae8d218ed7f08a3d7e56452dc9f050, ecb6e7b07c6e72d58aec155a65130695d12b41b8)

[tstraubinger]

These changes are ready for review. I've completely removed CppUnit from the AX tests but it remains a dependency at the top level. I think I'll put in a second pull request to remove it there as well, separately from this one. @Idclip @richhones @danrbailey

[tstraubinger]

I've created a secondary branch off of this one that further removes all mentions of CppUnit from the build dependencies and instructions. Shall I create a merge request into this branch, wait until this is merged, or just push the changes to this branch? https://github.com/tstraubinger/openvdb/tree/feature/remove_cppunit

[danrbailey]

I've created a secondary branch off of this one that further removes all mentions of CppUnit from the build dependencies and instructions. Shall I create a merge request into this branch, wait until this is merged, or just push the changes to this branch? https://github.com/tstraubinger/openvdb/tree/feature/remove_cppunit

Thanks, I'm fine to have these changes in this branch as they're all closely related. I've just approved the CI running, but note there are some conflicts, so this branch likely needs to be updated and the conflicts resolved which may affect the result of the CI.

[tstraubinger]

Changes have been rebased onto the current master branch and I've included removing CppUnit as a dependency. Whitespace that was causing a linting check to fail has also been removed. Unfortunately I don't know where to see other failed checks now that newer changes have been pushed.

[Idclip]

I've taken these changes and resolved the conflicts here: https://github.com/AcademySoftwareFoundation/openvdb/pull/2068

Closing this, will aim to get 2068 in as soon as possible, thanks again @tstraubinger!

[tstraubinger]

Acknowledged and much appreciated, thanks @Idclip!