Allow burning inscriptions

[casey]

It should be possible to burn inscriptions, to indicate that they can't be traded or transferred.

Add a subcommand ord wallet burn INSCRIPTION_ID which takes an inscrpition and sends it to an OP_RETURN. It should strip it down to the minimum size and return any postage to the user. Since the intention is to burn a sat, it the output size should be 1, not zero.

This should also allow including either an arbitrary UTF-8 string payload, or an arbitrary binary payload, and mark which one it is so they can be displayed correctly.