Give compareWith object mapping for SelectionModel same that of mat Select

### Feature Description

It's hard to map the object's other properties in the select something in the list using SelectionModel
Please give a option to map the object's unique key to the selection like we have it for Mat Select using compareWith

### Use Case

_No response_

Start by tracing SelectionModel and comparing its current selection behavior with Mat Select's compareWith option. Define how a unique object key should be supplied and verify that selection remains correct when object instances differ; done means the mapping option works for the stated object-selection use case and has coverage in the relevant tests.

Written by the indexing model from the issue text.