Add a generic dependency graph to smithy-utils

This adds a generic dependency graph to smithy-utils. This is intended
to be used to sort SmithyIntegrations, SmithyBuildPlugins, and
anything else that needs a topological sort.

Author: JordonPhillips

.changes/next-release/feature-d368237cdeb1655c7c10969e36c6aa3ca3b3034a.json

@@ -0,0 +1,5 @@
+{
+  "type": "feature",
+  "description": "Add a generic dependency graph to smithy-utils to be used for sorting various dependent objects, such as integrations and plugins.",
+  "pull_requests": []
+}

smithy-codegen-core/src/jmh/java/software/amazon/smithy/codegen/core/jmh/SmithyIntegrations.java

@@ -0,0 +1,4 @@
+package software.amazon.smithy.codegen.core.jmh;
+
+public class SmithyIntegrations {
+}