Reset back to Bitcoin PSBT and disable PSBT/PSET handling in wallet and
rpc.

This is just a reset to allow for PSBTv2 change and then a new and
improved PSET.

…to psbt module

SerializeToVector, UnserializeFromVector, DeserializeHDKeypaths, and SerializeHDKeypaths
were in sign.h where PSBT was originally implemented. Since all of the PSBT serialization
has moved to its own file, these functions should follow.

CExtPubKey does not store the version bytes for the extended public key.
We store these so that a CExtPubKey can be serialized and deserialized with
the same version bytes.

Previously these tests were using 0x0f as the field number. Changed to
use 0xf0 instead as it is unlikely we will hit that anytime soon.

With PSBTv2, some fields are not allowed in PSBTv2, and some are
required. Enforce those.

Fetches the PSBTv2 fields from PSBTv0's global unsigned tx. This allows
us to pretend everything internally is a PSBTv2 and makes things easier
to work with.

This is just a convenience and doesn't effect serialization.

Now that PSBTInput's track their own prevouts, there's no need for a
PSBT global function to fetch input specific data.

Function to compute the lock time for the transaction

A helper function for getting the unsigned transaction regardless of
psbt version.

The unique ID for PSBTv2 is different from v0. Use this function to get
the ID without requiring the caller to know the version number.

Helper for getting the PSBTInput COutPoint

If we are asked to make a PSBTv0, we may not necessarily have made an
unsigned transaction. So instead use GetUnsignedTx which will either
fetch one that already exists, or construct a new one from the stored
data. Internally we may be storing a PSBTv0 like a PSBTv2, but still
want to serialize those as v0.

Peg-ins don't have a typical UTXO. Instead we can get a "UTXO" using the
peg-in data.

The asset issuance details are added to createpsbt and
walletcreatefundedpsbt.

Instead of having an output_assets argument to createpsbt,
createrawtransaction, and walletcreatefundedpsbt, move the asset
specification into the outputs array itself. This also removes the
backwards compatibility of using a dict for outputs in createrawtransaction.

Output PSBTOutputs with blinding pubkey and index info from
ConstructTransaction so that these can be added to PSBTs later.

It is not invalid to have a value commitment and no explicit value. It
is only invalid to have neither for an output.

walletfillpsbtdata

These are all done by walletprocesspsbt

This test is for a condition that no longer matters. Prior to CA, there
was only the single value blinder for a transaction that sent unconf to
conf. This would necessitate setting that single blinding factor to 0,
which would make the single output not actually blinded. But with CA,
because each output has an additional blinding factor for the asset,
this issue no longer exists.

Helper function for getting a CTxOut for a PSBTOutput

It doesn't work, disable for now.