Add int range for touchscreen pointer id.

We are validating touch point id from ag/21078609, it's necessary to
enforce this from the API to prevent silent failures.

Test: atest VirtualInputDeviceConfigTest VirtualTouchscreenTest
Bug: 259554911

Change-Id: Ica8a3b5cc46517e6773c8c3a9d46e5606c63c00d
Merged-In: Ica8a3b5cc46517e6773c8c3a9d46e5606c63c00d