Add anonymous namespace to libcudf test source

[davidwendt]

Description

Uses anonymous namespace declaration on internal only functions and structures in the libcudf gtest source. This helps prevent odd nvcc compile errors like the one described in #17432

Closes #17432

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[copy-pr-bot]

Auto-sync is disabled for draft pull requests in this repository. Workflows must be run manually.

Contributors can view more details about this message here.

[davidwendt]

/ok to test

[davidwendt]

/ok to test

[vyasr]

Good change. Perhaps we should also be adding some symbol visibility markup to cudf::tests functions if they are causing further problems? It looks like the function Nghia originally ran into was in the test util and not a test.

[davidwendt]

Good change. Perhaps we should also be adding some symbol visibility markup to cudf::tests functions if they are causing further problems? It looks like the function Nghia originally ran into was in the test util and not a test.

I think that is something separate to consider but the visibility issue here was in the global namespace and not in the cudf::test one. I believe the error in the linked issue was just a unfortunate side-effect which would not have been fixed by hiding the cudf::test symbols.

[davidwendt]

/merge