Add log for showSoftInput called from Insets API

Add a debug log to identify calls to showSoftInput from Insets API.

Fix: 1865976
Test: manually using steps:
      1. Use an app like launcher that uses Insets API to show IME.
      2. dump using adb shell dumpsys input_method
      3. Verify log.
      4. use another app that shows IME using showSoftInput like gmail
      5. verify the log

Change-Id: I6ba0d3f7912855f31e033735557b44eeed3e6652