Move dumpViewInfo from InputMethodManager to InputMethodDebug

This a preperation CL before refactoring ImeFocusController.

To make dumpviewInfo can also be used in other IME related files
like ImeFocusController.

Also, removed unused method InputMethodDebug#objectToString.

This is just a mechanical refactoring and should not have any behavior
change.

Bug: 244504062
Test: build
Change-Id: I9d1a0c2b06e676e40b0e844edb18e8422a67b0ad