memory: Dehardcode the use of fixed memory range constants

The locations of these can actually vary depending on the address space
layout, so we shouldn't be using these when determining where to map
memory or be using them as offsets for calculations. This keeps all the
memory ranges flexible and malleable based off of the virtual memory
manager instance state.

src/core/hle/kernel/svc.cpp

@@ -51,8 +51,9 @@ static ResultCode SetHeapSize(VAddr* heap_addr, u64 heap_size) {
     }
 
     auto& process = *Core::CurrentProcess();
+    const VAddr heap_base = process.vm_manager.GetHeapRegionBaseAddress();
     CASCADE_RESULT(*heap_addr,
-                   process.HeapAllocate(Memory::HEAP_VADDR, heap_size, VMAPermission::ReadWrite));
+                   process.HeapAllocate(heap_base, heap_size, VMAPermission::ReadWrite));
     return RESULT_SUCCESS;
 }