Add new dumpsys command to dump the top resumed activity

The new command is invoked via

> adb shell dumpsys activity top-resumed

This command is used by foldables app compat QA team to extract
information about the resizability of the currently resumed activityf.

Bug: 155111946
Test: adb shell dumpsys activity top-resumed
Change-Id: I50b93ecb5deebd2461109b9e19ee9ae42f8ce15f