Organize notification classes in row/stack

No functional changes. Reorganized logic under either row, stack,
logging, or row/wrapper. Haven't moved all classes over since there's
some classes that create conflicts due to weird use of
package-private/protected (primarily waiting for HUN and shelf classes).

Test: built, ran, used notifications
Bug: 110802404
Change-Id: Ia2152603bdbeb12c522360193511946c843b9266