randomize GetTestDestinationDirectoryPath

[kasperk81]

lots of failures in theory tests such as

Microsoft.DotNet.Cli.Sln.List.Tests.GivenDotnetSlnList.WhenInvalidSolutionIsPassedItPrintsErrorAndUsage(solutionCommand: "sln") [FAIL]
      System.Exception : Test dir /private/tmp/helix/working/AD1509AD/w/BB910A35/e/testExecutionDirectory/WhenInvalidSo---F1406920_2 already exists

[kasperk81]

@edvilme this will fix the directory name conflict seen in #44570 when there are more than two theories relying on distinct naming _1 and _2 are not enough

[edvilme]

@edvilme this will fix the directory name conflict seen in #44570 when there are more than two theories relying on distinct naming _1 and _2 are not enough

Thanks for your contribution! This will be very helpful both for that PR and for further testing scenarios :)