nohelp-773227: Rationalize debug strings
nohelp-773227: Rationalize debug strings

The focus manager has always reported on why it made various focus
decisions, but the strings were mostly descriptive. By making them more
normalized, we can use the same strings in unit tests without things
looking strange.

joewalker/gcli,mozilla/gcli,mozilla/gcli,mozilla/gcli,joewalker/gcli