Add a process spawn syscall and use it to start a proc.

Also add a skeleton VirtualMemory manager to be used per process.

sys/test.cpp

@@ -1,7 +1,11 @@
 
 #include "zcall.h"
 
+constexpr uint64_t prog2 = 0x00000020'00000000;
+
 int main() {
   ZDebug("Testing");
+  ZProcessSpawn(prog2, 0x1000);
+  ZDebug("Return");
   return 0;
 }