Move PointerIconType to AIDL

to be shared between Java and C++.
The values of PointerIconStyle in Input.h and the constants in
PointerIcon.java are manually synced now.
This change introduces an AIDL file which can be used by both.

Bug: 235023317, 330827347
Test: presubmit
Change-Id: I01f31868e7c13270047673d97035783deaf0a7f6