Fix Workspace POM files processing ordering

Do not add any sorting forPOM files during 'MavenLemminxWorkspaceReader.addToWorkspace()' work.
The files are to be processed in the same order as they specified in method argument.
Any sorting is to be done before calling the method.

lemminx-maven/src/main/java/org/eclipse/lemminx/extensions/maven/MavenLemminxWorkspaceReader.java

@@ -16,11 +16,13 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
 import java.util.concurrent.ConcurrentHashMap;
@@ -155,7 +157,11 @@ public int hashCode() {
 	private final WorkspaceRepository repository;
 	private final MavenLemminxExtension plugin;
 
-	private SortedSet<File> toProcess = Collections.synchronizedSortedSet(new TreeSet<>(Comparator.comparingInt(file -> file.getAbsolutePath().length())));
+	// Don't add any sorting here, the files are to be processed exactly in the order they added.
+	// Any sorting is to be done before adding to this set
+	//
+	private Set<File> toProcess = Collections.synchronizedSet(new LinkedHashSet<File>());
+
 	private ThreadLocal<Boolean> skipFlushBeforeResult = new ThreadLocal<>();
 	private final PriorityBlockingQueue</*ResolveArtifactsAndPopulateWorkspaceRunnable*/Runnable> runnables = new PriorityBlockingQueue<>(1, DEEPEST_FIRST);
 	private final ExecutorService executor = new ThreadPoolExecutor(1, 1, 0, TimeUnit.MILLISECONDS, runnables);
@@ -278,6 +284,7 @@ private boolean attachedArtifactComparison(Artifact requested, Artifact attached
 
 	/**
 	 * Parses and adds a document for a given URI into the projects cache
+	 * Any sorting is to be done before the method is invoked.
 	 * 
 	 * @param uri An URI of a document to add
 	 * @param documents documents to add