[Kineto][Profiler] Rename Profiler post processing Index Key (#87477)
Summary: Rather than using the full name Profiler Event Index, use a shorten name Ev Idx. In the future, we should address this by adding a lookup table of short name to long name.
Test Plan: CI
Reviewed By: robieta, slgong-fb
Differential Revision: D40328758
Pulled By: aaronenyeshi
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87477
Approved by: https://github.com/chaekit
