Remove legacy fixed rotation pip

The methods are only used when pip change is not a transition.

Preserve WCT#scheduleFinishEnterPip because it is a TestApi that
can only be removed in a major release.

Bug: 365884835
Flag: EXEMPT remove unused code
Test: CtsWindowManagerDeviceWindow
Change-Id: Iff11b35e93d90b4c21d1bd47eac9580821f4d015