Anchor repository root probe

- Require the core source tree alongside the settings file when walking up for the repository root, so modded-common tests built inside a loader adapter no longer stop at that adapter's own settings file

core/src/test/java/art/arcane/iris/testsupport/ProjectPaths.java

@@ -69,7 +69,8 @@ public final class ProjectPaths {
         Path current = moduleRoot;
 
         while (current != null) {
-            if (Files.isRegularFile(current.resolve("settings.gradle"))) {
+            if (Files.isRegularFile(current.resolve("settings.gradle"))
+                    && Files.isDirectory(current.resolve("core/src/main/java"))) {
                 return current;
             }