core: fix native NEO ABI

This commit fixes T5 statediff at block #0. The reason in Management's
storage state. The diff occurs because of inconsistent NEO methods
order. See
https://github.com/neo-project/neo/issues/2766#issue-1257870089.

The current solution is to preserve C#'s order of methods to be
compatible with current testnet.

See also
https://docs.microsoft.com/ru-ru/dotnet/api/system.stringcomparer?view=net-6.0
and
https://stackoverflow.com/questions/28638714/easiest-method-to-orderby-a-string-using-stringcomparison-ordinal
for more details.

pkg/core/interop/context.go

@@ -207,7 +207,7 @@ func (c *ContractMD) AddMethod(md *MethodAndPrice, desc *manifest.Method) {
 	index := sort.Search(len(c.Manifest.ABI.Methods), func(i int) bool {
 		md := c.Manifest.ABI.Methods[i]
 		if md.Name != desc.Name {
-			return md.Name >= desc.Name
+			return strings.ToLower(md.Name) >= strings.ToLower(desc.Name)
 		}
 		return len(md.Parameters) > len(desc.Parameters)
 	})
@@ -236,7 +236,7 @@ func (c *ContractMD) GetMethodByOffset(offset int) (MethodAndPrice, bool) {
 func (c *ContractMD) GetMethod(name string, paramCount int) (MethodAndPrice, bool) {
 	index := sort.Search(len(c.Methods), func(i int) bool {
 		md := c.Methods[i]
-		res := strings.Compare(name, md.MD.Name)
+		res := strings.Compare(strings.ToLower(name), strings.ToLower(md.MD.Name))
 		switch res {
 		case -1, 1:
 			return res == -1

pkg/core/interop_system_core_test.go

@@ -967,3 +967,18 @@ func TestRuntimeCheckWitness(t *testing.T) {
 		})
 	})
 }
+
+// TestNativeGetMethod is needed to ensure that methods list has the same sorting
+// rule as we expect inside the `ContractMD.GetMethod`.
+func TestNativeGetMethod(t *testing.T) {
+	cfg := config.ProtocolConfiguration{P2PSigExtensions: true}
+	cs := native.NewContracts(cfg)
+	for _, c := range cs.Contracts {
+		t.Run(c.Metadata().Name, func(t *testing.T) {
+			for _, m := range c.Metadata().Methods {
+				_, ok := c.Metadata().GetMethod(m.MD.Name, len(m.MD.Parameters))
+				require.True(t, ok)
+			}
+		})
+	}
+}