Add PersistenceNotifierGuard take to offer/refund payments

This resolves an issue where offer and refund payments get delayed
while we wait for the `invoice_request`/`invoice` onion messages to
get sent. It further ensures we're likely to have the
`ChannelManager` persisted with the new payment info after
initiating the send/receive.

lightning/src/ln/channelmanager.rs

@@ -7772,6 +7772,8 @@ where
 		let invoice_request = builder.build_and_sign()?;
 		let reply_path = self.create_blinded_path().map_err(|_| Bolt12SemanticError::MissingPaths)?;
 
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
+
 		let expiration = StaleExpiration::TimerTicks(1);
 		self.pending_outbound_payments
 			.add_new_awaiting_invoice(
@@ -7833,6 +7835,8 @@ where
 		let amount_msats = refund.amount_msats();
 		let relative_expiry = DEFAULT_RELATIVE_EXPIRY.as_secs() as u32;
 
+		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
+
 		match self.create_inbound_payment(Some(amount_msats), relative_expiry, None) {
 			Ok((payment_hash, payment_secret)) => {
 				let payment_paths = self.create_blinded_payment_paths(amount_msats, payment_secret)