Hybrid device mode implemented as the current --mersenne=bydivisor CPU execution path. CPU path is now limited to CPU calculations, only.

PerfectNumbers.Core/ComputationDevice.cs

@@ -0,0 +1,8 @@
+namespace PerfectNumbers.Core;
+
+public enum ComputationDevice
+{
+	Cpu,
+	Hybrid,
+	Gpu,
+}