Record last keypress timestamp on physical keyboard while typing

Added method to record keypress timestamp while typing. This will be
used by touchpad to trigger additional palm rejection logic.

Bug: 301055381
Test: atest KeyboardInputMapperUnitTest
Change-Id: I4bbfe4c5fefc687a4901e46c9d4c6f832ec1a245
diff --git a/services/inputflinger/tests/InterfaceMocks.h b/services/inputflinger/tests/InterfaceMocks.h
index 05823cd..7394913 100644
--- a/services/inputflinger/tests/InterfaceMocks.h
+++ b/services/inputflinger/tests/InterfaceMocks.h
@@ -77,6 +77,9 @@
     MOCK_METHOD(void, setPreventingTouchpadTaps, (bool prevent), (override));
     MOCK_METHOD(bool, isPreventingTouchpadTaps, (), (override));
 
+    MOCK_METHOD(void, setLastKeyDownTimestamp, (nsecs_t when));
+    MOCK_METHOD(nsecs_t, getLastKeyDownTimestamp, ());
+
 private:
     int32_t mGeneration = 0;
 };