Introduce APIs necessary for IMEs to be able to distinguish when to show
virtual keyboard vs companion widget based on toolType.
IME receives click toolType in:
1. IMS#onUpdateEditorToolType(int toolType) for every showSoftInput()
called from IMM.
2. Initial value of toolType in EditorInfo#getInitialToolType().
Fix: 233108064
Bug: 210039666
Test: atest StylusHandwritingTest
Change-Id: I91ea9204ef62697b8942b0f350169382f18b3278