[REVIEW] Move DistanceType enum to RAFT

[wphicks]

Update all references from the DistanceType enum defined in cuML to the equivalent defined in RAFT. This change facilitates future re-use of this enum across Cython and prims code.

[GPUtester]

Please update the changelog in order to start CI tests.

View the gpuCI docs here.

[wphicks]

Linked RAFT PR: rapidsai/raft#73

[JohnZed]

Looks good, but can you target at 0.17 branch instead?

[divyegala]

@wphicks @JohnZed sorry to butt in, but I just noticed it: can we use namespace raft::distance for this instead of raft::linalg? Just to be consistent with the namespace it was in before (MLCommon::Distance)

[wphicks]

Yes of course! I'd actually meant to ask about what namespace made sense when I posted this. I'll update tomorrow.

[wphicks]

Oh and yep, I'll update to target 0.17 as well.

[divyegala]

Changes look mostly good to me, but let's run clang-tidy on the RAFT side of changes and cascade any naming convention diffs down here - I'll add the same comment there

[wphicks]

Looks like conda timed out in solving the environment. Retrying...

[wphicks]

rerun tests

[codecov-io]

Codecov Report

Merging #2918 into branch-0.17 will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           branch-0.17    #2918   +/-   ##
============================================
  Coverage        59.23%   59.23%           
============================================
  Files              142      142           
  Lines             8966     8966           
============================================
  Hits              5311     5311           
  Misses            3655     3655           

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[wphicks]

@divyegala This finally worked its way through CI (hooray!). Would you mind giving it one final review?

[divyegala]

LGTM!

[wphicks]

Took care of merge conflicts; no other changes

[wphicks]

Merge conflicts were causing too many problems to easily track down. Closing in favor of #3141.