Change back previous version hashing of 8 byte types

[yaeldekel]

In PR #5104 he hashing function of 8 byte numeric types was changed, but there still needs to be an unchanged implementation for old version models.

In addition, found a bug in ONNX conversion of hashing of keys that have underlying type different than uint.

[codecov]

Codecov Report

Merging #5152 into master will increase coverage by 0.01%.
The diff coverage is 82.27%.

@@            Coverage Diff             @@
##           master    #5152      +/-   ##
==========================================
+ Coverage   75.76%   75.77%   +0.01%     
==========================================
  Files         993      993              
  Lines      180746   180876     +130     
  Branches    19463    19477      +14     
==========================================
+ Hits       136944   137062     +118     
- Misses      38516    38521       +5     
- Partials     5286     5293       +7     

Flag	Coverage Δ
#Debug	75.77% <82.27%> (+0.01%)	⬆️
#production	71.70% <65.00%> (-0.01%)	⬇️
#test	88.87% <100.00%> (+0.02%)	⬆️

Impacted Files	Coverage Δ
src/Microsoft.ML.Data/Transforms/Hashing.cs	81.91% <65.00%> (-0.26%)	⬇️
test/Microsoft.ML.Tests/OnnxConversionTest.cs	99.38% <100.00%> (-0.07%)	⬇️
test/Microsoft.ML.Tests/Transformers/HashTests.cs	100.00% <100.00%> (ø)
....ML.AutoML/PipelineSuggesters/PipelineSuggester.cs	83.19% <0.00%> (-3.37%)	⬇️
src/Microsoft.ML.AutoML/Sweepers/Parameters.cs	84.32% <0.00%> (-0.85%)	⬇️
.../Microsoft.ML.Data/DataLoadSave/Text/TextLoader.cs	82.23% <0.00%> (-0.36%)	⬇️
...soft.ML.Data/DataLoadSave/Text/TextLoaderCursor.cs	89.58% <0.00%> (+0.16%)	⬆️
test/Microsoft.ML.Tests/TextLoaderTests.cs	96.26% <0.00%> (+0.51%)	⬆️
src/Microsoft.ML.Maml/MAML.cs	26.21% <0.00%> (+1.45%)	⬆️

[harishsk]