storage keys and values should be big endian (#277)

Storage keys and values are big endian. Keeping them LE was a pre-mature
optimization because for the contract itself it this is a no-op and thus
not observable. However we should consider the storage layout as part of
the contract ABI. The endianness of transient storage values are still
kept as-is.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/runner/src/specs.rs

@@ -106,14 +106,10 @@ impl SpecsAction {
         };
 
         for (key, expected) in storage {
-            let mut key = **key;
-            let mut expected = **expected;
-            key.reverse();
-            expected.reverse();
             actions.push(Self::VerifyStorage {
                 contract: account_pvm.clone(),
-                key,
-                expected,
+                key: **key,
+                expected: **expected,
             });
         }