Use LinkedHasMap in ModelAssembler in order to iterate over files con…

…sistently

smithy-model/src/main/java/software/amazon/smithy/model/loader/ModelAssembler.java

@@ -29,6 +29,7 @@
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -93,7 +94,7 @@ public final class ModelAssembler {
     private TraitFactory traitFactory;
     private ValidatorFactory validatorFactory;
     private boolean disableValidation;
-    private final Map<String, Supplier<InputStream>> inputStreamModels = new HashMap<>();
+    private final Map<String, Supplier<InputStream>> inputStreamModels = new LinkedHashMap<>();
     private final List<Validator> validators = new ArrayList<>();
     private final List<Node> documentNodes = new ArrayList<>();
     private final List<Model> mergeModels = new ArrayList<>();