Remove legacy window orientation changing state

This removes fields: mOrientationChanging, mOrientationChangeTimedOut
and methods: setOrientationChanging getOrientationChanging
Because getOrientationChanging always returns false since shell
transition is enabled. Then all related methods are no-op.

Flag: EXEMPT removed dead code
Bug: 365884835
Test: atest WindowStateTests
Change-Id: I1685158d4077c84f20b458105ccba924f44c70ec