Fix issue with debug TOSA dumps being overwritten (#5029)

Summary:
When a graph is partitioned into multiple partitions the Arm Backend overwrote the debug dump of TOSA intermediate files so that only the files for the last partition were available. To fix this the delegation tag is now appended to the file names.

Pull Request resolved: https://github.com/pytorch/executorch/pull/5029

Reviewed By: cccclai

Differential Revision: D62243216

Pulled By: digantdesai

fbshipit-source-id: f7c6a94a01a23bffa17c138ead455b4d28db1c6a