Fix C# pipeline build error

[skottmckay]

Description:
Can't use internal types in the external E2E test project. Throw standard C# exception instead.
Issue was introduced in #10428

Pipeline errors:

D:\a\_work\1\s\csharp\test\Microsoft.ML.OnnxRuntime.Tests.Common\TestDataLoader.cs(59,48): error CS0122: 'ErrorCode' is inaccessible due to its protection level [D:\a\_work\1\s\csharp\test\Microsoft.ML.OnnxRuntime.EndToEndTests\Microsoft.ML.OnnxRuntime.EndToEndTests.csproj]
D:\a\_work\1\s\csharp\test\Microsoft.ML.OnnxRuntime.Tests.Common\TestDataLoader.cs(59,27): error CS1729: 'OnnxRuntimeException' does not contain a constructor that takes 2 arguments [D:\a\_work\1\s\csharp\test\Microsoft.ML.OnnxRuntime.EndToEndTests\Microsoft.ML.OnnxRuntime.EndToEndTests.csproj]

Motivation and Context
Fix pipeline build error.