AutoTest: Avoid using costly containers

Replace several occurrences of QMap with QHash as we often do
not care about the order and use iterators instead of fetching
keys or values to iterate over them.

Change-Id: I5061a7e7e60fe259ac2aa31915f338a373e278d3
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>

src/plugins/autotest/testtreemodel.h

@@ -81,7 +81,7 @@ public:
     void markAllForRemoval();
     void markForRemoval(const QString &filePath);
     void sweep();
-    QMap<QString, QString> testCaseNamesForFiles(QStringList files);
+    QHash<QString, QString> testCaseNamesForFiles(QStringList files);
 
 signals:
     void testTreeModelChanged();