[release/3.0] Split out non concurrent test collections.

[michaelgsharp]

Backport of #6937 to release/3.0. Fixed version of closed pr #6947

/cc @michaelgsharp

Customer Impact

Improves the testing process for PR's to better facilitate us getting PR's out.

Testing

All tests pass with new changes and only test assemblies are changed.

Risk

None, only test assemblies are changed.

[ericstj]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f602581) 68.80% compared to head (a4c578d) 68.80%.

Additional details and impacted files

@@             Coverage Diff              @@
##           release/3.0    #6950   +/-   ##
============================================
  Coverage        68.80%   68.80%           
============================================
  Files             1240     1240           
  Lines           249604   249610    +6     
  Branches         25507    25507           
============================================
+ Hits            171740   171755   +15     
+ Misses           71265    71257    -8     
+ Partials          6599     6598    -1     

Flag	Coverage Δ
Debug	68.80% <100.00%> (+<0.01%)	⬆️
production	63.27% <ø> (+<0.01%)	⬆️
test	88.41% <100.00%> (+<0.01%)	⬆️

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

Files	Coverage Δ
...ft.ML.Core.Tests/UnitTests/TestResourceDownload.cs	0.00% <ø> (ø)
...ft.ML.TensorFlow.Tests/TensorFlowEstimatorTests.cs	98.50% <ø> (ø)
...t/Microsoft.ML.TensorFlow.Tests/TensorflowTests.cs	91.71% <ø> (ø)
test/Microsoft.ML.Tests/DatabaseLoaderTests.cs	94.41% <100.00%> (+0.17%)	⬆️
test/Microsoft.ML.TorchSharp.Tests/NerTests.cs	67.02% <ø> (ø)
...rosoft.ML.TorchSharp.Tests/ObjectDetectionTests.cs	100.00% <ø> (ø)
test/Microsoft.ML.TorchSharp.Tests/QATests.cs	40.50% <ø> (ø)
...oft.ML.TorchSharp.Tests/TextClassificationTests.cs	85.17% <ø> (ø)

... and 3 files with indirect coverage changes