Let layoutlib use new internal IMM APIs for edit mode

With this CL, layoutlib starts using new internal IMM APIs to make IMM
edit mode.

This allows us to remove a dependency on
InputMethodManager#getInstance(), which is soon deprecated because it
cannot be compatible with multi-display mode.

Bug: 115891476
Test: make layoutlib
Change-Id: Ibd76586b619450108d592629d02fe0c1dc0cccdd
4 files changed