ETDump cpp changes for intermediate logging (#1290)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/1290

All the ETDump changes needed for intermediate tensor logging. There is an additional method in `etdump_gen` now called `set_debug_buffer` that sets the debug buffer to which all intermediate and output tensors are logged to. This combined along with ETDump will need to be provided to the inspector API to analyze outputs/intermediate outputs.

Reviewed By: vmpuri

Differential Revision: D51402553

fbshipit-source-id: 28b24d4fe33a6503a42bb2ff43ea3d5e6f3f7f98