Fix LayerProtoHelper workaround to track layer ids

LayerProto shouldn't be created before checking duplication.

Will add unit tests for the deduping logic in a follow up change.

Bug: 335383156
Bug: 410180972
Test: atest SwitchToOverviewFromDesktopTest
Flag: EXEMPT bugfix

Change-Id: Ib6036140e0225d92b30b2d2b29d7ec403f626e33