Add shell-transitions inTransition check to getTouchOcclusionMode

This is the equivalent of legacy transitions isAnimating and is
used by inputflinger to know when to use opacity checks vs blind
occlusion blocking for untrusted touches.

Bug: 194233756
Test: atest WindowUntrustedTouchTest
Change-Id: I187c94ae55176d5369e5aaee995ccee251ac34b7