[region-isolation] When assigning RValues into memory, use tuple_addr_constructor instead of doing it in pieces.

I also included changes to the rest of the SIL optimizer pipeline to ensure that
the part of the optimizer pipeline before we lower tuple_addr_constructor (which
is right after we run TransferNonSendable) work as before.

The reason why I am doing this is that this ensures that diagnostic passes can
tell the difference in between:

```
x = (a, b, c)
```

and

```
x.0 = a
x.1 = b
x.2 = c
```

This is important for things like TransferNonSendable where assigning over the
entire tuple element is treated differently from if one were to initialize it in
pieces using projections.

rdar://117880194

lib/SIL/IR/SILPrinter.cpp

@@ -2223,7 +2223,7 @@ public:
     } else {
       *this << "[assign] ";
     }
-    *this << getIDAndType(TI->getDestValue());
+    *this << getIDAndType(TI->getDest());
 
     *this << " with (";