Add Customized Window Header support to CaptionWindowDecor.

Most of the code is borrowed from DesktopWindowDecor.

Bug: 352373408
Test: Manually using test app, atest CaptionWindowDecorationTests
Flag: EXEMPT Dev Tools only feature
Change-Id: Idd63b210f9be0516b781aca29449f6f82838bedb
4 files changed