Return EmittedDiagnostics in Session as a list of Diagnostic objects and not in human format

[ferranbt]

Describe the feature

Running this code:

let sess = Session::builder()
  .with_buffer_emitter(solar_interface::ColorChoice::Auto)
  .build();

let res = sess.enter(|| -> solar_interface::Result<()> {
  let mut pcx = solar_sema::ParsingContext::new(&sess);
  pcx.load_file(path).unwrap();
  pcx.parse_and_resolve()
});

sess.emitted_errors();

The function emitted_errors returns an EmittedDiagnostics object which is a human format representation of a list of Diagnostic objects.

I think the session object should not make the decision to return the errors in that specific format but return the Diagnostic objects itself and let the calling function decide how to format the result.

To give more colour to my use case, I was trying to write a debugger using solar and I need to format the diagnostics in a certain way.

Additional context

No response