[AWC] Make display-state CSS work on all platforms

There's variation between platforms on how they depict the window's
display-state and not all of them use `ui::WindowShowState`. Adding mapping to `ui::WindowShowState` despite the platform so that the CSS
value will work properly cross-platform.

TODO: It might make sense to create a new `ui::DisplayState` enum
instead that would then be purely used for the purposes of the
`display-state` @media feature CSS. However, if that's wanted, I'd
prefer implementing that in a follow-up as the feature not working is
currently blocking our partners and it's only internal refactoring which
which doesn't affect functionality.

I2P thread
https://groups.google.com/a/chromium.org/g/blink-dev/c/oCxWg8q_OQY/m/LUTw0T5cCQAJ

Public explainer is available @
https://github.com/ivansandrk/additional-windowing-controls/blob/main/awc-explainer.md

Private doc @ go/additional-windowing-controls

Bug: 1466855, 1466851, b:288265319, b:307194715
Change-Id: I25ee3640d935f0d2a0c4741865fdefbb6b8b9271
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4954859
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Sonja Laurila <laurila@google.com>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1217470}