gh-132657: Add free-threading scaling benchmark for copy.copy and copy.deepcopy

[eendebakpt]

In this branch two benchmarks for the free-threading scaling are added. They are not completely microbenchmarks (they test multiple aspects of the free-threaded performance).

• Issue: copy.copy and copy.deepcopy scale poorly with free-threading #132657

[colesbury]

This looks good, but in general my preference is to add these benchmarks when we fix the scaling issue. I think of these like regression tests, and having a mix of "passing" and "failing" cases makes it harder to notice regressions.

[eendebakpt]

Thanks for the feedback. I suspect we will only need one of the two benchmarks as a regression test (as the reason for not scaling seems to be the same). Once we have a better scaling, I will remove one of the tests.

[eendebakpt]

@colesbury The deepcopy benchmark was already merged in #142843. The copy benchmark overlaps for a large part with the deepcopy benchmark (e.g. both have the same potential FT bottlenecks). Unless there are reasons to add the copy as well I suggest we close this PR.

[colesbury]

Sounds good to me