Cursed Inscriptions

From https://github.com/casey/ord/issues/2045:

casey commented 3 weeks ago:

It would be desirable to modify ord to recognize the following:

- Multiple inscriptions per transaction, for efficient batching
- Inscriptions on inputs after the first, which is useful for collections
- Multiple inscriptions on the same sat, so that the entire history
  of a sat doesn't need to be checked to determine if a new inscription
  is valid
- Inscriptions with unrecognized even headers, so that new even headers
  don't cause upgraded clients to disagree about inscription numbers

An idea for how to do this is:

- Modify ord to recognize the above currently invalid inscriptions,
  including retroactively in old blocks, but consider these new
  inscriptions "cursed" and assign them negative inscription numbers.
  Since they would not receive positive inscription numbers, they
  would not disrupt existing inscription numbers
- At a future, pre-announced block height X, new inscriptions that
  would have been cursed before X are now not cursed, or "blessed",
  and receive a positive inscription number instead of a negative one.

The reasoning for this strange scheme is as follows:

- I don't like changing old inscription numbers by fiat.
- I want to make previously invalid inscriptions appear on
   ordinals.com as soon as possible, and giving them a negative
  inscription number allows that with minimal changes to the code.
  Hopefully making them visible will help further the conversation,
  let people see how many exist, and make everything more concrete.
- Having a pre-announced block height at which previously invalid
  inscriptions would now be valid allows ample time for everyone to
  upgrade.
- Negative inscription numbers would always be perma-unstable.
- We could use this same scheme again in the future. Some new way of
  making inscriptions is desirable, they initially receive negative
   numbers, and at a pre-announced flag day they enter the main sequence.