Revert "Deprecate drag-corner-to-resize-pip on phones"

This reverts commit 43cd5bfd.

Reason for revert: We now want this feature for Android Desktop Mode.

Recall: http://recall/clips/0257acc3-edf5-4910-bda5-ff163be7b419

Bug: 375054477
Test: atest PinnedStackTests PipResizeGestureHandlerTest
Test: m -j ArcSystemUI
Flag: TBA

Change-Id: If639834e377a705dfbe8d6eee7bda988b61edb32