RSN 44 - Moving older RAPIDS conda packages to a `legacy` label

Overview

RAPIDS will move certain older conda packages in the rapidsai conda channel under a new label: legacy. These packages will still be available by adding -c rapidsai/label/legacy to installation and search commands.

By moving these packages out of the main portion of the channel, newer RAPIDS conda environments will be solvable with channel_priority: strict, speeding up environment solve times and providing stronger correctness guarantees.

All RAPIDS conda install commands for RAPIDS versions v23.04+ will continue to work without any user intervention.

This change will occur concurrently with the release of RAPIDS v25.04.

Impact

RAPIDS environments installed using conda or mamba, for environments older than RAPIDS v23.04 will fail to install unless -c rapidsai/label/legacy is added to the installation command.

e.g. if you are creating an environment like:

mamba create -n rapids-23.02 -c rapidsai -c conda-forge -c nvidia rapids=23.02 python=3.10 'cuda-version>=11.4,<=11.8'

you will need to instead run

mamba create -n rapids-23.02 -c rapidsai -c rapidsai/label/legacy -c conda-forge -c nvidia rapids=23.02 python=3.10 'cuda-version>=11.4,<=11.8'