from feedback by Gleb and Joost.

Instead of implicitly detecting whether or not an OP_VAULT/OP_UNVAULT
spend is a recovery spend by scanning outputs for matching
scriptPubKeys, explicitly indicate recoveries by requiring a witness
stack element that is either -1 in the case of no recovery OR
corresponds to an output index that is the recovery output.

Thanks to Vojtěch Strnad for most of this.

Since constraints on unauthorized recovery transaction structure exist
only to avoid pinning, make them a matter of policy and not consensus.

copypasta FTW

Co-authored-by: kallewoof <kalle.alm@gmail.com>

Adds AJ and Greg as co-authors

This change makes the amount being revaulted (if any) explicit to avoid
issues surfaced by AJ Towns (e.g. multiple compatible vault inputs
duplicating triggers and revaults to confuse the old deferred check
logic).

Pseudocode is also provided for the deferred checks, and their inline
validation description has been changed to be more faithful to the
implementation - we make mention of queueing deferred checks, and then
later describe the algorithm used to aggregate and perform them.

Allow trigger/recovery output nValues to exceed the amounts supplied by
constituent vault inputs. This allows future compatibility for e.g.
trigger collateral.

Co-authored-by: sanket1729 <sanket1729@gmail.com>

Co-authored-by: Antoine Poinsot <darosior@protonmail.com>