[e2e] use alternative `copy tree` function to tolerate output directory that already exists (#21869)
[e2e] use alternative `copy tree` function to tolerate output directory that already exists (#21869)

Many release tests have error messages when copying results with `shutil.copytree()`. e.g.
https://buildkite.com/ray-project/periodic-ci/builds/2511#131c0d22-61a3-4dcf-b80a-de37b68ec591/139-450

This PR tries to make the copying process tolerate existing destination directory. There is logic to remove the destination directory, but I'm not sure why it failed.

This error should not be failing the tests though.
ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray