[RONs] Move right icon to right available space

The expander is not shown for RONs. This CL positions right icon to the right available space from expander by respecting its horizontal paddings.

Bug: 393369727
Test: Post a RON with long header content and large icon and see large icon is shown on the right available space.
Flag: com.android.systemui.ui_rich_ongoing_force_expanded
Change-Id: I37279967d0719d004a2e0ba1e409d49b8aa4935b