coverlet: Coverage causes hangs

Hi,

When adding coverage for .NET Framework, it’s causing hangs. It works fine on .NET Core: https://dev.azure.com/onovotny/GitBuilds/_build/results?buildId=2203&view=logs&j=12f1170f-54f2-53f3-20dd-22fc7dff55f9

This commit has the changes: https://github.com/onovotny/bc-csharp/commit/5ddb17530b4175ce31092ac671d2ed496c2ecd06

Here’s the command that fails, when on .NET Framework: https://github.com/onovotny/bc-csharp/commit/5ddb17530b4175ce31092ac671d2ed496c2ecd06

Seems like it’s happening with .NET Core too: https://dev.azure.com/onovotny/GitBuilds/_build/results?buildId=2204&view=logs&j=12f1170f-54f2-53f3-20dd-22fc7dff55f9&t=bfbec40a-1b5e-5690-b870-859627cad0c0&l=20

Should be able to repro with dotnet test -f netcoreapp2.1 ...

Repro steps:

Clone: https://github.com/onovotny/bc-csharp Checkout commit: 4a401ed22df13ef61b2bb7a306ee8a083167f1c6 Go to crypto\test Run dotnet test -f netcoreapp2.1 and see that it passes. About 1.5 min on my machine Run dotnet test -f netcoreapp2.1 -s ..\..\CodeCoverage.runsettings

Tests are taking much longer to run (never complete) and fail in some cases.

I think it’s struggling on this test: https://github.com/onovotny/bc-csharp/blob/netstandard/crypto/test/src/math/ec/test/ECPointPerformanceTest.cs#L176

Perhaps with some of the random number generators in use there?