Switch to DataLoader::load in runtime (#4217)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4217

Description
- Makes the appropriate changes in runtime code to deprecate DataLoader::Load in favor of DataLoader::load with SegmentInfo.
- Adds tests for the load function

Follow-ups planned in diff stack
- (D59606243) Currently `program.cpp` is passing in a hardcoded`"backend_segment"` as the descriptor, but in a follow-up will pass in the actual backend id.
- Test `Constant` segment case

Diff stack:
- (  ) [[1/n][executorch] Introduce new DataLoader::load() with segment info](https://www.internalfb.com/diff/D59399538?dst_version_fbid=2979141262226992)
- (**x**) [[2/n][executorch] Switch to DataLoader::load in runtime](https://www.internalfb.com/diff/D59594142)
- (  ) [[3/n][executorch] Pass in correct backend id into data load from runtime](https://www.internalfb.com/diff/D59606243)

Reviewed By: dbort

Differential Revision: D59594142

fbshipit-source-id: d579ea2eb9ee4b7f6e38877b156f340292efef30