Correct regex escape logic

* Fixes #7776

Implement QRegularExpression::escape within Tools::convertToRegex to allow usage on older Qt versions.

Also wrap EXACT_MODIFIER patterns in a non-capture group to prevent misinterpreted regex.

tests/TestTools.h

@@ -31,6 +31,8 @@ private slots:
     void testValidUuid();
     void testBackupFilePatternSubstitution_data();
     void testBackupFilePatternSubstitution();
+    void testEscapeRegex();
+    void testEscapeRegex_data();
     void testConvertToRegex();
     void testConvertToRegex_data();
 };