Throw when PCA generates invalid eigenvectors

[antoniovs1029]

Fixes microsoft/NimbusML#497

As discussed there, the problem is that when PCA generates eigenvectors with NaN values, a cryptic exception is thrown on NimbusML during prediction and not during training. It's thrown during prediction because to do prediction NimbusML saves the model to disk and loads it back, and during deserialization there's a check that prevents loading eigenvectors that contain NaNs.

In this PR I'm adding an exception to the constructor of PcaModelParameters so that a more readable exception is thrown during training of either NimbusML or ML.NET, so there's no need to wait until prediction for NimbusML to throw it.

[antoniovs1029]

The same check is done when deserializing, so it's ok to also add it in the constructor:

machinelearning/src/Microsoft.ML.PCA/PcaTrainer.cs

Lines 506 to 509 in a769365

	var vi = ctx.Reader.ReadFloatArray(_dimension);
	Host.CheckDecode(vi.All(FloatUtils.IsFinite));
	_eigenVectors[i] = new VBuffer<float>(_dimension, vi);
	_meanProjected[i] = VectorUtils.DotProduct(in _eigenVectors[i], in _mean);

The custom message was requested by the customer that opened the original issue on NimbusML.

[codecov]

Codecov Report

Merging #5349 into master will decrease coverage by 0.07%.
The diff coverage is 96.15%.

@@            Coverage Diff             @@
##           master    #5349      +/-   ##
==========================================
- Coverage   74.04%   73.97%   -0.08%     
==========================================
  Files        1019     1019              
  Lines      189949   189975      +26     
  Branches    20429    20429              
==========================================
- Hits       140651   140531     -120     
- Misses      43786    43918     +132     
- Partials     5512     5526      +14     

Flag	Coverage Δ
#Debug	73.97% <96.15%> (-0.08%)	⬇️
#production	69.74% <100.00%> (-0.10%)	⬇️
#test	87.68% <95.65%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
test/Microsoft.ML.Tests/AnomalyDetectionTests.cs	99.29% <95.65%> (-0.71%)	⬇️
src/Microsoft.ML.PCA/PcaTrainer.cs	81.87% <100.00%> (+0.16%)	⬆️
...c/Microsoft.ML.FastTree/Utils/ThreadTaskManager.cs	79.48% <0.00%> (-20.52%)	⬇️
...osoft.ML.KMeansClustering/KMeansPlusPlusTrainer.cs	83.60% <0.00%> (-7.27%)	⬇️
src/Microsoft.ML.Data/Training/TrainerUtils.cs	66.86% <0.00%> (-3.82%)	⬇️
....ML.AutoML/PipelineSuggesters/PipelineSuggester.cs	83.19% <0.00%> (-3.37%)	⬇️
...crosoft.ML.StandardTrainers/Standard/SdcaBinary.cs	85.23% <0.00%> (-3.33%)	⬇️
...L.AutoML/TrainerExtensions/TrainerExtensionUtil.cs	84.71% <0.00%> (-1.66%)	⬇️
src/Microsoft.ML.Sweeper/AsyncSweeper.cs	71.42% <0.00%> (-1.37%)	⬇️
...crosoft.ML.StandardTrainers/Optimizer/Optimizer.cs	71.96% <0.00%> (-1.16%)	⬇️
... and 10 more