Release patch release 1.1.1 with faster CPU performance

[hcho3]

• Port CPU performance improvement Fix release degradation #5720
• Bump version to 1.1.1

Closes #5666

@trivialfis @SmirnovEgorRu @ShvetsKS The CI system will momentarily produce a wheel file. I will post the link once it's available. You should be able to try it and check for performance improvement.

[hcho3]

Here is the new wheel: https://s3-us-west-2.amazonaws.com/xgboost-nightly-builds/PR-5732/xgboost-1.1.1%2B39744a4c113c73b49e9a02e4a86c917609c50b2e-py3-none-manylinux2010_x86_64.whl

[codecov-commenter]

Codecov Report

Merging #5732 into release_1.1.0 will not change coverage.
The diff coverage is n/a.

@@              Coverage Diff               @@
##           release_1.1.0    #5732   +/-   ##
==============================================
  Coverage          82.48%   82.48%           
==============================================
  Files                 11       11           
  Lines               2598     2598           
==============================================
  Hits                2143     2143           
  Misses               455      455           

Impacted Files	Coverage Δ
python-package/xgboost/core.py	77.79% <ø> (ø)

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[SmirnovEgorRu]

@hcho3, got it.
@ShvetsKS, could, you, please, check the wheel for fixing the performance issues?

[ShvetsKS]

@hcho3, got it.
@ShvetsKS, could, you, please, check the wheel for fixing the performance issues?

Seems it works fine.