[input_pipeline] Drop wake leases for keyboard reports.

This CL changes the KeyboardBinding to drop all the wake leases for
keyboard reports. This ensures that no wake leases will be held
within input_pipeline.

Test: Manually tested. See b/481865507
Bug: 481865507
Bug: 482049480
Change-Id: I4e12e5ec97277b4318eacb188d3f6296487cb61f
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1497619
Reviewed-by: Caroline Liu <carolineliu@google.com>
Commit-Queue: Yilong Li <liyl@google.com>