Use cached launcher shelf KCA before entering PiP

For entering PiP in button navigation mode, we would allow Launcher
shelf height change to update the destination bounds in the middle of
entering animation.

This works in most cases, but if the animation has progressed beyond a
certain point, such Launcher shelf height change would cause the
animation to suddenly change its moving direction, e.g. move up.

In this change, we used the cached launcher shelf height to calculate
the destination bounds, to make the animation independent from the
Launcher shelf height update timing.

Flag: EXEMPT bugfix
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/fTeZwHHX3hGd6mRqSIjgp9
Bug: 326287104
Test: Enter PiP in button nav, both folded and unfolded
Test: atest --iteration 10  WMShellFlickerTestsPip1 -- --test-arg \
      com.android.tradefed.testtype.AndroidJUnitTest:instrumentation-arg\
      :filter-tests:="com.android.wm.shell.flicker.pip.\
      AutoEnterPipWithSourceRectHintTest#pipLayerMovesTowardsRightBottomCorner[ROTATION_0_3_BUTTON_NAV]"
Change-Id: I97f67824f9f153eba5bc34d090e7a12e4d634c03