Set of public keys in SigningTxData

[grarco]

namada/crates/sdk/src/signing.rs

Lines 69 to 73 in c0b9f68

	pub struct SigningTxData {
	/// The address owning the transaction
	pub owner: Option<Address>,
	/// The public keys associated to an account
	pub public_keys: Vec<common::PublicKey>,

We could change the collection of public keys used for multisig public keys to a HashSet to avoid useless duplicates and/or the need to filter them out.

A similar approach should be taken for the generate_tx_signatures function used to produce offline signatures