Forward port - v12 - Externalize Auto-Export LocationMapper entries to a resource file

Forward-port the fix of CMS-10753 as excerpted below:
Even if we're going to replace the auto-export feature by something better in v12, it might be safer to simply forward-port the fix until the whole auto-export submodule can be removed safely in the future.

AFAIK auto-export has hardcoded knowledge about how to split certain parts of the repository into files and folders (see the ENTRIES in https://code.onehippo.org/cms-community/hippo-cms/blob/master/automatic-export/repository/src/main/java/org/onehippo/cms7/autoexport/LocationMapper.java).

The hard-coded entries looks like something we can improve very easily even in v11. As William mentioned and Engineering is refactoring it totally with YAML, it must be not a good idea to spend too much time on improving it in v11.

But, it really looks like a low-hanging fruit improvement. For example, one hard-coded entry is:

    static {
        // /hippo:namespaces/example
        String[] nodePatterns = new String[] {"/hippo:namespaces/" + NAME};
        String[] propertyPatterns = new String[] {"/hippo:namespaces/" + NAME + "/" + NAME};
        String contextNode = "/hippo:namespaces/$1";
        String file = "namespaces/$1.xml";
        ENTRIES.add(new Entry(nodePatterns, propertyPatterns, contextNode, file));
        // ... SNIP ...
    }

If we change the static block to load those entries from classpath resource file (e.g, classpath:org/onehippo/cms7/autoexport/LocationMapper.xml) like the following example:

location-mapper.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE location-mapper [
  <!ENTITY NAME "([^/\u005B\u005D\|\*]+(?:\u005B\d+\u005D)?)">
  <!ENTITY ANY "(.*)">
]>
<location-mapper>
  <entries>
    <entry>
      <node-patterns>
        <node-pattern>/hippo:namespaces/&NAME;</node-pattern>
      </node-patterns>
      <property-patterns>
        <property-pattern>/hippo:namespaces/&NAME;/&NAME;</property-pattern>
      </property-patterns>
      <context-node>/hippo:namespaces/$1</context-node>
      <file>namespaces/$1.xml</file>
    </entry>
  </entries>
  <!-- ... -->
</location-mapper>

So, the idea is:

• We do NOT change or try to improve the current auto-export behaviors at all in v11 branch,
• But simply externalize the 'static hard-coded initialization of mapping entries to a classpath XML resource file.
• So, possibly developers can override the classpath XML resource file to control the entries.
• If we do have proper unit tests to ensure the backward compatibility even with this kind of simple improvement, I think it should be fine.
• This is in the same pattern (externalizing hard-coded parts to a classpath resource file) as https://issues.onehippo.com/browse/REPO-1630.

Wouldn't it be a low-hanging fruit in v11 branch, or would it be better to just wait for v12 and upgrades someday later?