Fix Android touch hover and cancellation

[huacnlee]

Summary

Apply the iOS touch cleanup from #3 to Android. After touch release/cancellation and every momentum frame, move the synthetic pointer outside the window and emit MouseExited so hover does not remain on the last control. Preserve original coordinates for click and scroll dispatch.

Handle ACTION_CANCEL independently: discard queued coalesced scroll, reset velocity, stop inertia, and emit ScrollWheel(Cancelled) for an active scroll. Never turn cancellation into a tap or fling, and ignore stray moves with no active touch.

Add regression tests and update an existing test to use the renamed gpu_specs API.

Test Plan

• Android arm64/API 31 cargo-ndk library check passed.
• Built the Android unit-test executable and ran touch tests on an Android API 34 arm64 emulator: 5 passed.
• Tests cover tap coordinates, pending-tap cancellation, coalesced-scroll cancellation, and post-momentum hover cleanup.
• This verification covers platform event dispatch; Android app UI testing is ongoing separately.