feat(snack-bar): Close Icon

[james-schwartzkopf]

Feature Description

The m3 spec here: https://m3.material.io/components/snackbar/specs shows an Icon (optional close affordance)

It would be nice if this could be added to the SimpleSnackBar and had a way to enable from MatSnackBar.open

Use Case

This would be a nice alternative to having a 'Dismiss' action on error messages, etc.