Add STATE_CLEAR and STATE_TOUCH_INTERACTING to TouchExplorer.

STATE_CLEAR represents an initial state where no fingers are down. STATE_TOUCH_INTERACTING is where we try to detect the user's intent.

Bug: 136131815
Test: atest CtsAccessibilityServiceTestCases FrameworksServicesTests:TouchExplorerTest
Change-Id: Ifac5ab2556d5d16e6326fec1f92064cb6987b519