Rearranges part of AddAnonInputs_Inner into separate helper functions so it's easier to understand and also to reuse the code elsewhere. I'm not sure I fully understood the code enough to properly name the helper functions, but here they are:

• ArrangeBlinds
  • Places the real inputs and creates dummy entries for the ring.
  • Optionally adds temporary dummy sigs.
• GetKeyImage
  • Attaches the key image for a real input.
  • I made this take one at a time for ease of calling from elsewhere.
• SetBlinds
  • Does some further stuff to the blinds.