contracts: Fix some minor bugs around instantiation (#8879)

* Fix output of wrongly outputted error

The "Tombstoned a contract that is below the subsistence threshold: {:?}" was
triggered when too few balance was provided. It was a false alarm.

* Fix return of wrong code_len

* Split up `NotCallable` into more fine grained errors

* Fix typos in docs

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

* RentNotPayed -> RentNotPaid

* Fix typo: payed -> paid

It is OK to change the in-storage field name because:

1. The SCALE encoding is not based on names only on position.
2. The struct is not public (only to the crate).

Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

substrate/frame/contracts/src/benchmarking/mod.rs

@@ -409,7 +409,7 @@ benchmarks! {
 
 	// We benchmark the costs for sucessfully evicting an empty contract.
 	// The actual costs are depending on how many storage items the evicted contract
-	// does have. However, those costs are not to be payed by the sender but
+	// does have. However, those costs are not to be paid by the sender but
 	// will be distributed over multiple blocks using a scheduler. Otherwise there is
 	// no incentive to remove large contracts when the removal is more expensive than
 	// the reward for removing them.
@@ -435,7 +435,7 @@ benchmarks! {
 		instance.ensure_tombstone()?;
 
 		// the caller should get the reward for being a good snitch
-		// this is capped by the maximum amount of rent payed. So we only now that it should
+		// this is capped by the maximum amount of rent paid. So we only now that it should
 		// have increased by at most the surcharge reward.
 		assert!(
 			T::Currency::free_balance(&instance.caller) >