[Floonet] add feature for height locked kernels (#2168)

* add feature for height locked kernels

* add function to compute kernel features appropriate for lock height, and use it

* only sign kernel-features relevant fields; refactor Features

* simplify invalid kernel logic

* remove unused height arg to reward::output and run some rustfmt

* replace nested if/else by match

servers/src/mining/mine_block.rs

@@ -173,7 +173,7 @@ fn burn_reward(block_fees: BlockFees) -> Result<(core::Output, core::TxKernel, B
 	let keychain = ExtKeychain::from_random_seed().unwrap();
 	let key_id = ExtKeychain::derive_key_id(1, 1, 0, 0, 0);
 	let (out, kernel) =
-		crate::core::libtx::reward::output(&keychain, &key_id, block_fees.fees, block_fees.height)
+		crate::core::libtx::reward::output(&keychain, &key_id, block_fees.fees)
 			.unwrap();
 	Ok((out, kernel, block_fees))
 }