SSE41 version of Hadamard transform

[brianpopow]

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Description

This adds a SSE41 version of the Hadamard transform which is used during lossy webp encoding.
Relates to #1786

Profiling results:

Before:

After:

note the number of calls is halfed, because the sse version does two transformas at once

[codecov]

Codecov Report

Merging #1810 (2e52890) into master (c8f6d75) will decrease coverage by 0.19%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1810      +/-   ##
==========================================
- Coverage   87.31%   87.12%   -0.20%     
==========================================
  Files         936      936              
  Lines       48015    48085      +70     
  Branches     6034     6035       +1     
==========================================
- Hits        41924    41892      -32     
- Misses       5092     5190      +98     
- Partials      999     1003       +4     

Flag	Coverage Δ
unittests	87.12% <100.00%> (-0.20%)	⬇️

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

Impacted Files	Coverage Δ
src/ImageSharp/Formats/Webp/Lossy/LossyUtils.cs	100.00% <100.00%> (ø)
...ageSharp/Formats/Webp/Lossless/PredictorEncoder.cs	89.22% <0.00%> (-9.08%)	⬇️
.../ImageSharp/Formats/Webp/Lossless/LosslessUtils.cs	88.68% <0.00%> (-8.86%)	⬇️

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[antonfirsov]

LGTM.