[REVIEW] Moving linalg decomp to RAFT namespaces

[divyegala]

This moves the following:

1. linalg/eig.cuh
2. linalg/svd.cuh
3. linalg/qr.cuh

Major changes involve API change (adding a handle param to the function signature, and removing cublasHandle_t, allocator, etc.). This change is performed in all files mentioned above

[GPUtester]

Please update the changelog in order to start CI tests.

View the gpuCI docs here.

[codecov-io]

Codecov Report

Merging #2906 into branch-0.17 will increase coverage by 0.01%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           branch-0.17    #2906      +/-   ##
===============================================
+ Coverage        58.86%   58.87%   +0.01%     
===============================================
  Files              143      143              
  Lines             9004     9004              
===============================================
+ Hits              5300     5301       +1     
+ Misses            3704     3703       -1     

Impacted Files	Coverage Δ
...l/_thirdparty/sklearn/preprocessing/_imputation.py	62.50% <0.00%> (+0.40%)	⬆️

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[drobison00]

Minor updates, and a couple formatting questions; other than that LGTM.

[drobison00]

Looks good!

[dantegd]

approval needed from cpp-codeowners