kernel/vm_manager: Rename HeapAllocate to SetHeapSize

Makes it more obvious that this function is intending to stand in for
the actual supervisor call itself, and not acting as a general heap
allocation function.

Also the following change will merge the freeing behavior of HeapFree
into this function, so leaving it as HeapAllocate would be misleading.

src/core/hle/kernel/svc.cpp

@@ -175,8 +175,7 @@ static ResultCode SetHeapSize(VAddr* heap_addr, u64 heap_size) {
     }
 
     auto& vm_manager = Core::System::GetInstance().Kernel().CurrentProcess()->VMManager();
-    const auto alloc_result = vm_manager.HeapAllocate(heap_size);
-
+    const auto alloc_result = vm_manager.SetHeapSize(heap_size);
     if (alloc_result.Failed()) {
         return alloc_result.Code();
     }

src/core/hle/kernel/vm_manager.cpp

@@ -256,7 +256,7 @@ ResultCode VMManager::ReprotectRange(VAddr target, u64 size, VMAPermission new_p
     return RESULT_SUCCESS;
 }
 
-ResultVal<VAddr> VMManager::HeapAllocate(u64 size) {
+ResultVal<VAddr> VMManager::SetHeapSize(u64 size) {
     if (size > GetHeapRegionSize()) {
         return ERR_OUT_OF_MEMORY;
     }

src/core/hle/kernel/vm_manager.h

@@ -380,7 +380,7 @@ public:
     /// Changes the permissions of a range of addresses, splitting VMAs as necessary.
     ResultCode ReprotectRange(VAddr target, u64 size, VMAPermission new_perms);
 
-    ResultVal<VAddr> HeapAllocate(u64 size);
+    ResultVal<VAddr> SetHeapSize(u64 size);
     ResultCode HeapFree(VAddr target, u64 size);
 
     ResultCode MirrorMemory(VAddr dst_addr, VAddr src_addr, u64 size, MemoryState state);