Log when TouchInputMapper drops touch

Today, it's possible for InputReader to drop touch without any logs,
which makes it difficult to debug issues like 'dropped touches', either
in the field, or during test failures.

These logs will make it explicit that touch is being dropped. Unless
virtual key is pressed, this should not occur under normal device
operation.

Bug: 396796958
Test: atest inputflinger_tests
Flag: EXEMPT refactor
Change-Id: Ibbd69e8380d0d4d9e6e6d07936dc98ab958baf2a