Provide a RetryingExecutionStrategy that relies on the new DbException.IsTransient

[roji]

Now that DbException.IsTransient has been merged into System.Data (dotnet/runtime#34817), we can now provide an execution strategy implementation which relies on it. Providers where the property is implemented should be able to just use this strategy as-is.

Note: since the property is only available in .NET 5.0, this isn't likely to be very useful until we drop support for previous versions.