Allow descriptor wallet creation

[rajarshimaitra]

The current RpcApi defaults to creating legacy wallet. Is it possible to set an extra option to choose to create a descriptor wallet instead??

rust-bitcoincore-rpc/client/src/client.rs

Lines 272 to 291 in 657eebd

	fn create_wallet(
	&self,
	wallet: &str,
	disable_private_keys: Option<bool>,
	blank: Option<bool>,
	passphrase: Option<&str>,
	avoid_reuse: Option<bool>,
	) -> Result<json::LoadWalletResult> {
	let mut args = [
	wallet.into(),
	opt_into_json(disable_private_keys)?,
	opt_into_json(blank)?,
	opt_into_json(passphrase)?,
	opt_into_json(avoid_reuse)?,
	];
	self.call(
	"createwallet",
	handle_defaults(&mut args, &[false.into(), false.into(), into_json("")?, false.into()]),
	)
	}

Also would be really helpful to open up importdescriptors call to RpcApi..

[dunxen]

Looks like this is dependent on #199