Have pmd-xml Lexer in line with other antlr grammars

- The package is no longer antlr4, but ast, as is in all other modules
 - We keep a deprecated proxy for backwards compatibility
 - We annotate the generated classes as such to ignore them from
   coverage reports

pmd-xml/pom.xml

@@ -45,6 +45,28 @@
                     </parameter>
                 </configuration>
             </plugin>
+
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-antrun-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <id>antlr-cleanup</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>run</goal>
+                        </goals>
+                        <configuration>
+                            <target>
+                                <ant antfile="${antlr4.ant.wrapper}" target="cpd-language">
+                                    <property name="lang-name" value="XML" />
+                                    <property name="lang-id" value="xml" />
+                                </ant>
+                            </target>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
         </plugins>
     </build>
     <dependencies>

pmd-xml/src/main/java/net/sourceforge/pmd/lang/xml/antlr4/XMLLexer.java

@@ -0,0 +1,17 @@
+package net.sourceforge.pmd.lang.xml.antlr4;
+
+import org.antlr.v4.runtime.CharStream;
+
+/**
+ * Backwards compatible bridge. The XMLLexer was moved to align it with other PMD modules.
+ * This class will be removed in PMD 8.0.0.
+ * Use {@link net.sourceforge.pmd.lang.xml.ast.XMLLexer} directly instead.
+ *
+ * @deprecated
+ */
+@Deprecated
+public class XMLLexer extends net.sourceforge.pmd.lang.xml.ast.XMLLexer {
+    public XMLLexer(CharStream input) {
+        super(input);
+    }
+}

pmd-xml/src/main/java/net/sourceforge/pmd/lang/xml/cpd/XmlCpdLexer.java

@@ -8,7 +8,7 @@ import org.antlr.v4.runtime.CharStream;
 import org.antlr.v4.runtime.Lexer;
 
 import net.sourceforge.pmd.cpd.impl.AntlrCpdLexer;
-import net.sourceforge.pmd.lang.xml.antlr4.XMLLexer;
+import net.sourceforge.pmd.lang.xml.ast.XMLLexer;
 
 /**
  * <p>Note: This class has been called XmlTokenizer in PMD 6</p>.