Indexing / Add related record title to the full text search

Some catalogues link records to others which can be in the same catalogue or in remote sites.

Links are encoded using 
```xml
<gmd:source uuidref="https://ec.europa.eu/eurostat/cache/metadata/en/env_nwat_esms.htm"
 xlink:title="Water statistics on national level (env_nwat)" 
xlink:href="https://ec.europa.eu/eurostat/cache/metadata/en/env_nwat_esms.htm"/>
```
and the `xlink:title` may contain the remote record title (or the customized title cf. #7324)

This adds the related records title to the full text search.

Sample record
https://sdi.eea.europa.eu/catalogue/srv/eng/catalog.search#/metadata/04b55edf-9a98-4123-87ab-7845af61d07d
With that change searching for `env_nwat` will return the record due to the source dataset.

web/src/main/webResources/WEB-INF/data/config/index/records.json

@@ -1778,7 +1778,8 @@
             "type": "keyword"
           },
           "title": {
-            "type": "keyword"
+            "type": "keyword",
+            "copy_to": "any.common"
           },
           "origin": {
             "type": "keyword"