Require approval to run CI on draft PRs

[bdice]

By default, CI runs on draft PRs. This leads to many CI runs that may be unnecessary.

With this PR's change to .github/copy-pr-bot.yaml, an /ok to test comment from a trusted user is required to trigger CI on draft PRs. Non-draft PRs will run CI by default, assuming that all commits are signed by trusted users. Otherwise an /ok to test is required (as before) -- see the copy-pr-bot docs at https://docs.gha-runners.nvidia.com/apps/copy-pr-bot/ for more information.

Part of rapidsai/build-planning#123.

[bdice]

/pyenv/versions/3.10.15/lib/python3.10/site-packages/cudf/_lib/__init__.py:4: in <module>
    from . import (
parquet.pyx:1: in init cudf._lib.parquet
    ???
E   ValueError: pylibcudf.io.types.ColumnInMetadata size changed, may indicate binary incompatibility. Expected 112 from C header, got 48 from PyObject

These failures are unrelated. I suspect that two different builds of pylibcudf were used at different points in the build process. This should resolve itself, if I'm right. However, I don't think it is worth rerunning all CI for that to be tested, so I will request an admin-merge.