Add debug_buffer_size for ETDumpGen in pybindings (#4063)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4063

We want to be able to set the debug buffer when using the python API
of Executorch. This allows storing the intermediate outputs of each
instruction in the program.

Add `debug_buffer_size` as a parameter to specify that, and a new parameter
for `write_etdump_result_to_file` in case that debug buffer was non-zero.

Reviewed By: tarun292, dbort

Differential Revision: D57363557

fbshipit-source-id: 7c8f83b11dc71712722ace12b44bf872f924ed75