[C++] Check for duplicate buffers in IPC writer

[bkietz]

Describe the enhancement requested

Some operations may produce data which reuses buffers. This is particularly true with the addition of string view. It should be straightforward and cheap to detect based on pointer identity, then that buffer could be written just once and the corresponding offset reused. This should be doable without any change to the IPC format, which is not prescriptive about whether buffers overlap.

Component(s)

C++