Add new `TouchpadInputMapper` class

This will replace `MultiTouchInputMapper` and `SingleTouchInputMapper`
for touchpad devices, and will be the wrapper for the gestures library.

Bug: 251196347
Test: connect Apple Magic Trackpad 2 to device, check logs come out
Test: atest inputflinger_tests
Change-Id: Ia8ee1779a40c6c6f98373e114c040bf13b7f213d
diff --git a/services/inputflinger/reader/Android.bp b/services/inputflinger/reader/Android.bp
index 46e86de..551ad7a 100644
--- a/services/inputflinger/reader/Android.bp
+++ b/services/inputflinger/reader/Android.bp
@@ -51,6 +51,7 @@
         "mapper/SingleTouchInputMapper.cpp",
         "mapper/SwitchInputMapper.cpp",
         "mapper/TouchInputMapper.cpp",
+        "mapper/TouchpadInputMapper.cpp",
         "mapper/VibratorInputMapper.cpp",
         "mapper/accumulator/CursorButtonAccumulator.cpp",
         "mapper/accumulator/CursorScrollAccumulator.cpp",