Plumb a Delegate Metadata Parser (#1356)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/1356

Add the ability to pass in an optional parser for Delegate Debug Metadata.
- Result is available via `Event.delegate_debug_metadatas`

The parser takes in a list of DelegateDebugMetadata (sourced from ETDump) and returns a `Dict[str, Any]`

In addition, the parsed result can optionally be provided via `toDataFrame()`

Reviewed By: tarun292

Differential Revision: D51805808

fbshipit-source-id: 986349bd2374e6884d22565ddcda7eebfb53ad34