Support @left marker

By default cutouts are centered and support a @right marker to allow
them to be right aligned. Let's also support left alignment by
introducing a @left marker.

Test: atest DisplayCutoutTest
Test: manual
Bug: 143222961
Bug: 145707162
Change-Id: Ic5a645bd9f0513f3665f31c8b0f1861585bf30e6
Merged-In: Ic5a645bd9f0513f3665f31c8b0f1861585bf30e6
(cherry picked from commit 6e9636c5)