Sort static overlays by priority

Since static overlays are still managed by the native layer, we must
order the overlays during the initial scan so the are put into the
AssetManager in the correct order.

Bug: 121002654
Test: build_success and manual verification of ordering
Change-Id: Id46baed8f836c3b4b86d19d58aee5fd06ff0b762
2 files changed