runtime: vmoffsets must be checked in reverse order (#4253)

When adding shared memory, memories owned by the module were added to a
`owned_memories` array placed immediately after the `defined_memories`
array. When checking the size of each array with `region_sizes`, the
size of `defined_memories` and `owned_memories` were checked in this
order. But `region_sizes` is iterating through the fields in the reverse
order. This change reverses the field order to fix the associated fuzz
bug.

crates/environ/src/vmoffsets.rs

@@ -251,8 +251,8 @@ impl<P: PtrSize> VMOffsets<P> {
         calculate_sizes! {
             defined_anyfuncs: "module functions",
             defined_globals: "defined globals",
-            defined_memories: "defined memories",
             owned_memories: "owned memories",
+            defined_memories: "defined memories",
             defined_tables: "defined tables",
             imported_globals: "imported globals",
             imported_memories: "imported memories",