Unify dense and sparse tests

[levsnv]

The pull request includes changes from #4328. To view only changes pertinent to unifying tests, see
https://github.com/levsnv/cuml/pull/3/files?diff=unified&w=1

[canonizer]

Nice work! Approved, provided that the comments are addressed.

Review details in levsnv#3.

[wphicks]

Beautiful! LGTM

[wphicks]

@gpucibot merge

[levsnv]

rerun tests

15:16:13 gpuCI logger » [12/17/21 23:16:14]
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15:16:13 |    Checking if ccache tarball exists    |
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15:16:15 Found existing ccache tarball: rapidsai/cuml/pull-request/4417/ccache/ccache-ubuntu18.04-cuda11.5-py3.7-aarch64.tar
15:16:36 tar: Skipping to next header
15:16:42 tar: Exiting with failure status due to previous errors
15:16:42 Build step 'Execute shell' marked build as failure
15:17:02 [Set GitHub commit status (universal)] ERROR on repos [GHRepository@1bba4d9d[nodeId=MDEwOlJlcG9zaXRvcnkxNTI2MTY4MDI=,description=cuML - RAPIDS Machine Learning Library,homepage=,name=cuml,fork=false,archived=false,size=152711,milestones={},language=Cuda,commits={},source=<null>,parent=<null>,isTemplate=false,url=https://api.github.com/repos/rapidsai/cuml,id=152616802,nodeId=<null>,createdAt=2018-10-11T15:45:35Z,updatedAt=2021-12-17T21:30:16Z]] (sha:5679fe1) with context:gpuCI/cuml/build/python-arm64/3.7/cuda/11.5