Migrate to NVKS for amd64 CI runners

[bdice]

This migrates amd64 CI jobs to use L4 GPUs from the NVKS cluster.

xref: https://github.com/rapidsai/build-infra/issues/184

[msarahan]

8.971 error    libmamba Could not solve for environment specs
8.971     The following package could not be installed
8.971     └─ rapids =25.4 * does not exist (perhaps a typo or a missing channel).

Need nightly channel?

[bdice]

8.971 error    libmamba Could not solve for environment specs
8.971     The following package could not be installed
8.971     └─ rapids =25.4 * does not exist (perhaps a typo or a missing channel).

Need nightly channel?

This is using the nightly channel, but we're missing a rapids=25.04 metapackage on the nightly channel. I requested help from ops.

[bdice]

Blocked until a rapids=25.04 metapackage can be created, which is in turn blocked by rapidsai/xgboost-feedstock#77.

[jameslamb]

pre-emptively giving you a ci-codeowners approval because I approve of the matrix changes, so you can merge this whenever we have rapids=25.04 packages.

[jakirkham]

Blocked until a rapids=25.04 metapackage can be created, which is in turn blocked by rapidsai/xgboost-feedstock#77

The XGBoost PR has been merged. So that should unblock building the rapids metapackages

[jakirkham]

Tracking rapids metapackages in issue: rapidsai/integration#750

[jakirkham]

Metapackages are now up

Have restarted CI

[jakirkham]

Approving as well

Bradley please feel free to merge whenever CI passes

[bdice]

/merge

[bdice]

cuML seems broken. I guess we can retry this next week.