split_view: Fix UMA device orientation reports

In this CL, we make sure |orientation_| is actually the device
orientation rather than split view orientation by adding
`IsDisplayLayoutHorizontal()` to display_util.cc|h

--Affected metrics
`Ash.SplitView.EntryPoint.DeviceOrientation` (crrev.com/c/2960585),
`Ash.SplitView.OrientationInSplitView`,
`Ash.Window.Snap.DeviceOrientation` (crrev.com/c/3100865), and
`Ash.SplitView.DeviceOrientation.{DeviceUIMode}`
should report device |orientation_|.

`ash_unittests --gtest_filter=*SplitViewControllerPortraitTest*` and
`*AcceleratorControllerTestWithClamshellSplitView*`

Test: Manual and
Bug: 1243542
Change-Id: Ida1472ab8b931f34c895f3d0cd6b181884ff574c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3119413
Commit-Queue: Cattalyya Nuengsigkapian <cattalyya@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/main@{#916207}