Fix bundle icon sizing

It needs to be treated like a notification icon rather than status bar
icon

Test: manual (post one bundle and one silent notif, make sure both show
status bar)
Test: Increase text size, make sure bundle icon spacing doesn't change
Test: validate content descriptions for notification and bundle status
bar icons
Fixes: 428513924
Flag: com.android.systemui.notification_bundle_ui

Change-Id: I283697e58f47fa467921cdae21d075967ee8fafe