Enrich AssertFailedException with tested value(s)

[inikulshin]

E.g. add an expected and actual values:

var ex = new AssertFailedException(...);
ex.Data["assertionName"] = "AreEqual";
ex.Data["expected"] = expected;
ex.Data["actual"] = actual;
throw ex;

https://learn.microsoft.com/en-us/dotnet/api/system.exception.data?view=net-9.0

[nohwnd]

+1 At least for expected and actual we have fields in MTP to ship it to error view that can compare the values, would be very helpful for vscode where the diff view is present and can show the values, and hopefully test explorer would add it as well, I've discussed it with the team in the past but it did not go anywhere, so it might be worth re-opening.