Fix disabled state of CallStyle buttons to make them look/act disabled

TLDR; Call Style Buttons does not seem disabled when they dont have intent.

In Android Notifications, Button's enabled state is coupled with the action intent. It means when there is an intent, the button is enabled. Otherwise, it is disabled.
We are handling this for normal action button by creating specific layout for disabled view but not for emphasized buttons. We follow the similar approach here to mitigate
this visual issue.

Bug: 265021861
Test: We can verify the change by observing visual effect on the Call Style Notification.

Change-Id: I2427f613e6051bf887dfe99c6caead1521b1e661