[REVIEW] Fixing umap gtest failure under cuda 11.2.

[cjnolet]

Closes #3406.

There's a couple things to note in this PR:

1. There is a kernel in the UMAP gtest that computes an L1 between two different embeddings and it wasn't using atomics for the addition so we may have just not been seeing these failures until now
2. The Python code wasn't failing because it's using random init instead of spectral. I'm going to open an issue in RAFT to investigate why the spectral init differs from run to run with the same inputs even when random seed is set.

[cjnolet]

This also depends on rapidsai/raft#193

[viclafargue]

Thanks for looking into this, great fix! Forgot about atomics... sorry for this.

[dantegd]

Just wanted to leave a comment that one CI job showed a small doxygen issue, so that it doesn't block things later:

Generating docs for c/workspace/cpp/include/cuml/cluster/spectral.hpp:38: error: The following parameter of 
ML::Spectral::fit_embedding(const raft::handle_t &handle, int *rows, int *cols, float *vals, int nnz, int n, int n_components, float 
*out, unsigned long long seed=1234567) is not documented:
17:47:37   parameter 'seed' (warning treated as error, aborting now)

[codecov-io]

Codecov Report

Merging #3696 (dbc509f) into branch-0.19 (fd9ec89) will increase coverage by 2.31%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.19    #3696      +/-   ##
===============================================
+ Coverage        80.70%   83.02%   +2.31%     
===============================================
  Files              227      227              
  Lines            17615    17712      +97     
===============================================
+ Hits             14217    14706     +489     
+ Misses            3398     3006     -392     

Flag	Coverage Δ
dask	45.62% <ø> (+0.63%)	⬆️
non-dask	75.11% <ø> (+2.19%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
python/cuml/__init__.py	95.58% <ø> (+0.20%)	⬆️
...cuml/_thirdparty/sklearn/preprocessing/__init__.py	100.00% <ø> (ø)
...on/cuml/_thirdparty/sklearn/preprocessing/_data.py	64.40% <ø> (+1.29%)	⬆️
...hirdparty/sklearn/preprocessing/_discretization.py	83.33% <ø> (-0.88%)	⬇️
...l/_thirdparty/sklearn/preprocessing/_imputation.py	85.54% <ø> (+22.74%)	⬆️
python/cuml/_thirdparty/sklearn/utils/extmath.py	56.89% <ø> (ø)
...cuml/_thirdparty/sklearn/utils/skl_dependencies.py	80.00% <ø> (+26.07%)	⬆️
...ython/cuml/_thirdparty/sklearn/utils/validation.py	18.41% <ø> (-4.04%)	⬇️
python/cuml/cluster/__init__.py	100.00% <ø> (ø)
python/cuml/cluster/agglomerative.pyx	96.47% <ø> (ø)
... and 181 more

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[cjnolet]

@gpucibot merge