[Reflection] Change ReadBytesFunction to return a pointer rather than copying data, and adjust its users accordingly.

rdar://problem/37538580

include/swift/Remote/InProcessMemoryReader.h

@@ -42,9 +42,9 @@ class InProcessMemoryReader final : public MemoryReader {
     return true;
   }
 
-  bool readBytes(RemoteAddress address, uint8_t *dest, uint64_t size) override {
-    std::memcpy(dest, address.getLocalPointer<void>(), (size_t) size);
-    return true;
+  std::tuple<const void *, std::function<void()>>
+    readBytes(RemoteAddress address, uint64_t size) override {
+    return std::make_tuple(address.getLocalPointer<void>(), []{});
   }
 };