Enforce block connection ordering in unit and functional tests

This expands the assertions on block ordering to apply to
`#[cfg(test)]` builds in addition to normal builds, requiring that
unit and functional tests have syntactically-valid (ie the previous
block hash pointer and the heights match the blocks) blockchains.

This requires a reasonably nontrivial diff in the functional tests
however it is mostly straightforward changes.

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -3302,16 +3302,10 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
 		let _persistence_guard = PersistenceNotifierGuard::new(&self.total_consistency_lock, &self.persistence_notifier);
 
-
-		// This assertion should be enforced in tests, however we have a number of tests that
-		// were written before this requirement and do not meet it.
-		#[cfg(not(test))]
-		{
-			assert_eq!(*self.last_block_hash.read().unwrap(), header.prev_blockhash,
-				"Blocks must be connected in chain-order - the connected header must build on the last connected header");
-			assert_eq!(self.latest_block_height.load(Ordering::Acquire) as u64, height as u64 - 1,
-				"Blocks must be connected in chain-order - the connected header must build on the last connected header");
-		}
+		assert_eq!(*self.last_block_hash.read().unwrap(), header.prev_blockhash,
+			"Blocks must be connected in chain-order - the connected header must build on the last connected header");
+		assert_eq!(self.latest_block_height.load(Ordering::Acquire) as u64, height as u64 - 1,
+			"Blocks must be connected in chain-order - the connected header must build on the last connected header");
 		self.latest_block_height.store(height as usize, Ordering::Release);
 		*self.last_block_hash.write().unwrap() = block_hash;