Add log for events dropped by InputState

Before this CL, events could be silently dropped. This is because
InputState acts as a "verifier" in a way - if an incorrect stream is
detected, it doesn't crash, but simply skips the event.

In this CL, log is added so that we learn about these drops if something
goes wrong.
In theory, this should never happen because the InputState should never
receive an inconsistent stream to begin with.

Bug: 281806933
Note: the actual test will be added in a later patch
Test: m inputflinger_tests && adb sync data && adb shell -t data/nativetest64/inputflinger_tests/inputflinger_tests --gtest_filter="*MultiplePointersWithRotatingWindow"
Change-Id: I1a0b417872d03e3b1b11dd68b9bbe3a0dc057a14