select: selectionChange should also emit item in id mode

[saithis]

No description provided.

[Yirica]

Looked into this for a short while. My impressions:

• With the current usage of mat-select selectionChange, the item would have to be loaded from the dataSource. Can't estimate the workload of this solution.

• Another option is to use onSelectionChange of mat-option and emit it from select-data.component to select.component. This makes it easy to access the item of the option in the change event. But this event triggers quite often on a single change. Restricting the emit by the provided "isUserInput" doesn't seem correct.

• Adding the item to the value in id mode doesn't seem like the way to go either.