Fix PackageInstaller icon resizing issue

Bug: 114719061
Test: builds, installed the app and verified visually

TL;DR;; when main icon is rendered, there's no guarantee that the icon
will be rendered in 48dp view. For the inset to be applied proportionally,
percentage should be used instead of static dp unit.

Change-Id: Iacfcf7a5a2aa430c70c5db7c803267cf7eb5ad45