Add call to IL2CPP_il2cpp_object_unbox in ILGeneratorEx to fix incorrect call for reference value type parameter

[Steve-xmh]

When a parameter is a reference of Il2CppSystem.ValueType, the generated code doesn't correctly unboxed, which will let the game or program got a wrong pointer and crash the program. This issue is trying to fix that by calling il2cpp_object_unbox to get actual reference pointer of the value.

Only tested on my mod of Taiko no Tatsujin - Rhythm Festival Steam PC version. I don't have enough time for further testing so I don't know whether it will break something or not.

Old interop code generated:

[CallerCount(3)]
[CachedScanResults(RefRangeStart = 51506, RefRangeEnd = 51509, XrefRangeStart = 51500, XrefRangeEnd = 51506, MetadataInitTokenRva = 0, MetadataInitFlagRva = 0)]
public unsafe bool GetCurrentOnpu([In] ref GameDrawInfo drawInfo, int prefabType, ref OnpuBase onpu)
{
  IL2CPP.Il2CppObjectBaseToPtrNotNull((Il2CppObjectBase) this);
  System.IntPtr* numPtr1 = stackalloc System.IntPtr[3];
  // Still not an actual pointer
  numPtr1[0] = IL2CPP.Il2CppObjectBaseToPtrNotNull((Il2CppObjectBase) drawInfo);
  *(System.IntPtr*) ((System.IntPtr) numPtr1 + checked (new System.IntPtr(1) * sizeof (System.IntPtr))) = (System.IntPtr) &prefabType;
  System.IntPtr num1 = (System.IntPtr) numPtr1 + checked (new System.IntPtr(2) * sizeof (System.IntPtr));
  System.IntPtr ptr = IL2CPP.Il2CppObjectBaseToPtr((Il2CppObjectBase) onpu);
  System.IntPtr* numPtr2 = &ptr;
  *(System.IntPtr*) num1 = (System.IntPtr) numPtr2;
  System.IntPtr exc;
  System.IntPtr num2 = IL2CPP.il2cpp_runtime_invoke(OnpuPlayer.NativeMethodInfoPtr_GetCurrentOnpu_Private_Boolean_byref_GameDrawInfo_Int32_byref_OnpuBase_0, IL2CPP.Il2CppObjectBaseToPtrNotNull((Il2CppObjectBase) this), (void**) numPtr1, ref exc);
  Il2CppInterop.Runtime.Il2CppException.RaiseExceptionIfNecessary(exc);
  ref OnpuBase local = ref onpu;
  System.IntPtr pointer = ptr;
  OnpuBase onpuBase = pointer == System.IntPtr.Zero ? (OnpuBase) null : new OnpuBase(pointer);
  local = onpuBase;
  return *(bool*) IL2CPP.il2cpp_object_unbox(num2);
}

New interop code generated:

[CallerCount(3)]
[CachedScanResults(RefRangeStart = 51506, RefRangeEnd = 51509, XrefRangeStart = 51500, XrefRangeEnd = 51506, MetadataInitTokenRva = 0, MetadataInitFlagRva = 0)]
public unsafe bool GetCurrentOnpu([In] ref GameDrawInfo drawInfo, int prefabType, ref OnpuBase onpu)
{
  IL2CPP.Il2CppObjectBaseToPtrNotNull((Il2CppObjectBase) this);
  System.IntPtr* numPtr1 = stackalloc System.IntPtr[3];
  // Unbox here
  numPtr1[0] = IL2CPP.il2cpp_object_unbox(IL2CPP.Il2CppObjectBaseToPtrNotNull((Il2CppObjectBase) drawInfo));
  *(System.IntPtr*) ((System.IntPtr) numPtr1 + checked (new System.IntPtr(1) * sizeof (System.IntPtr))) = (System.IntPtr) &prefabType;
  System.IntPtr num1 = (System.IntPtr) numPtr1 + checked (new System.IntPtr(2) * sizeof (System.IntPtr));
  System.IntPtr ptr = IL2CPP.Il2CppObjectBaseToPtr((Il2CppObjectBase) onpu);
  System.IntPtr* numPtr2 = &ptr;
  *(System.IntPtr*) num1 = (System.IntPtr) numPtr2;
  System.IntPtr exc;
  System.IntPtr num2 = IL2CPP.il2cpp_runtime_invoke(OnpuPlayer.NativeMethodInfoPtr_GetCurrentOnpu_Private_Boolean_byref_GameDrawInfo_Int32_byref_OnpuBase_0, IL2CPP.Il2CppObjectBaseToPtrNotNull((Il2CppObjectBase) this), (void**) numPtr1, ref exc);
  Il2CppInterop.Runtime.Il2CppException.RaiseExceptionIfNecessary(exc);
  ref OnpuBase local = ref onpu;
  System.IntPtr pointer = ptr;
  OnpuBase onpuBase = pointer == System.IntPtr.Zero ? (OnpuBase) null : new OnpuBase(pointer);
  local = onpuBase;
  return *(bool*) IL2CPP.il2cpp_object_unbox(num2);
}

The il2cpp method signature from IDA as reference:

bool OnpuPlayer__GetCurrentOnpu(
        OnpuPlayer_o *this,
        Blittables_GameDrawInfo_o *drawInfo,
        int32_t prefabType,
        OnpuBase_o **onpu,
        const MethodInfo *method);