Bech32 for displaying the nonce

[NicolasDorier]

Right now, we are showing the nonce as an hex string.
I think this should be changed as fast as possible.

The reason is, when taproot activate, we will want to move from ECDSA Adaptor sigs to Schnorr Adaptor sigs, by doing so, the attestations of the oracle will be different, so an oracle need a way to signal to users what they will be attesting.

Using Bech32, allows us to include this information in the hrp or inside the data, and on top of that make it encoding the nonce shorter.

[benthecarman]

The reason is, when taproot activate, we will want to move from ECDSA Adaptor sigs to Schnorr Adaptor sigs, by doing so, the attestations of the oracle will be different

What the oracle signs shouldn't be different for if the users are using ECDSA or Schnorr, it should be able to be independent of that.