Camera2: Rework the FPS range vs. FPS single setting detection

Give up on current approach of writing out consistent FPS values
into parameters that will be read back by the app.

- Preserve app's latest set parameters exactly, and compare against
  them when detecting if a new FPS range or single FPS value has been
  selected.

- Since get() returns exactly what was set(), it doesn't matter if the
  app calls getParameters() before its next setParameters(), in terms
  of retriggering FPS selection logic. Before, the behavior varied
  depending on whether the app re-read the parameters.

- As before, if app changes both range and single FPS in a single set
  call, the range set wins. Otherwise, the value that has changed more
  recently is used.

Bug: 11570973
Change-Id: I72b5e60c3f60e88d55127dd1bda87e26eaf929c6