*: drop support for old on-chain assets

You no longer can transfer them, so creating/renewing/storing doesn't make
much sense.

pkg/core/interops_test.go

@@ -34,15 +34,6 @@ func TestUnexpectedNonInterops(t *testing.T) {
 	funcs := []func(*interop.Context, *vm.VM) error{
 		accountGetBalance,
 		accountGetScriptHash,
-		assetGetAdmin,
-		assetGetAmount,
-		assetGetAssetID,
-		assetGetAssetType,
-		assetGetAvailable,
-		assetGetIssuer,
-		assetGetOwner,
-		assetGetPrecision,
-		assetRenew,
 		attrGetData,
 		attrGetUsage,
 		blockGetTransaction,