Validate code when scheduling uprades from registrar (#3232)

Currently, anyone can registrar a code that exceeds the code size limit
when performing the upgrade from the registrar. This PR fixes that and
adds a new test to cover this.

cc @bkchr @eskimor

polkadot/primitives/src/lib.rs

@@ -57,8 +57,8 @@ pub use v6::{
 	UpgradeRestriction, UpwardMessage, ValidDisputeStatementKind, ValidationCode,
 	ValidationCodeHash, ValidatorId, ValidatorIndex, ValidatorSignature, ValidityAttestation,
 	ValidityError, ASSIGNMENT_KEY_TYPE_ID, LEGACY_MIN_BACKING_VOTES, LOWEST_PUBLIC_ID,
-	MAX_CODE_SIZE, MAX_HEAD_DATA_SIZE, MAX_POV_SIZE, ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE,
-	PARACHAINS_INHERENT_IDENTIFIER, PARACHAIN_KEY_TYPE_ID,
+	MAX_CODE_SIZE, MAX_HEAD_DATA_SIZE, MAX_POV_SIZE, MIN_CODE_SIZE,
+	ON_DEMAND_DEFAULT_QUEUE_MAX_SIZE, PARACHAINS_INHERENT_IDENTIFIER, PARACHAIN_KEY_TYPE_ID,
 };
 
 #[cfg(feature = "std")]

polkadot/primitives/src/v6/mod.rs

@@ -362,6 +362,9 @@ pub const PARACHAINS_INHERENT_IDENTIFIER: InherentIdentifier = *b"parachn0";
 /// The key type ID for parachain assignment key.
 pub const ASSIGNMENT_KEY_TYPE_ID: KeyTypeId = KeyTypeId(*b"asgn");
 
+/// Compressed or not the wasm blob can never be less than 9 bytes.
+pub const MIN_CODE_SIZE: u32 = 9;
+
 /// Maximum compressed code size we support right now.
 /// At the moment we have runtime upgrade on chain, which restricts scalability severely. If we want
 /// to have bigger values, we should fix that first.