cache path for solr embedded is not properly escaped on Windows

The dataDir property in <perm>\xwiki\store\solr\search\core.properties" is not being written in the proper format. This showed up specifically because backslashes require escape on Windows, but not using the java.util.Properties standard library class to write properties files may cause other yet to be encountered formatting issues. I have a pull request coming with the necessary code change to "xwiki-platform/xwiki-platform-search-solr-api/src/main/java/org/xwiki/search/solr/internal/EmbeddedSolr.java" and that adds a regression test.

See also https://forum.xwiki.org/t/15-10-10-version-startup-service-error/14684/3

Versions are: 12.10, 12.10.1, 12.10.10, 12.10.11, 12.10.2, 12.10.3, 12.10.4, 12.10.5, 12.10.6, 12.10.7, 12.10.8, 13.0, 13.1, 13.1-rc-1, 13.10, 13.10-rc-1, 13.10.1, 13.10.10, 13.10.11, 13.10.2, 13.10.3, 13.10.4, 13.10.5, 13.10.6, 13.10.7, 13.10.8, 13.10.9, 13.2, 13.2-rc-1, 13.3, 13.3-rc-1, 13.4, 13.4-rc-1, 13.4.1, 13.4.4, 13.4.5, 13.4.6, 13.5, 13.5-rc-1, 13.6, 13.6-rc-1, 13.7, 13.7-rc-1, 13.8-rc-1, 13.9, 14.0-rc-1, 14.1, 14.10, 14.10.1, 14.10.10, 14.10.11, 14.10.12, 14.10.13, 14.10.16, 14.10.17, 14.10.2, 14.10.20, 14.10.21, 14.10.6, 14.10.8, 14.10.9, 14.2.1, 14.3, 14.3-rc-1, 14.3.1, 14.4, 14.4-rc-1, 14.4.1, 14.4.2, 14.4.3, 14.4.4, 14.4.7, 14.4.8, 14.6, 14.7-rc-1, 14.8, 15.0, 15.0-rc-1, 15.1-rc-1, 15.10-rc-1, 15.10.1, 15.10.10, 15.10.11, 15.10.12, 15.10.13, 15.10.14, 15.10.15, 15.10.2, 15.10.6, 15.10.7, 15.10.8, 15.2-rc-1, 15.3-rc-1, 15.4, 15.5, 15.5-rc-1, 15.5.1, 15.5.2, 15.5.3, 15.5.4, 15.6-rc-1, 15.7, 15.8, 15.8-rc-1, 15.9, 16.0.0, 16.1.0, 16.1.0-rc-1, 16.10.0, 16.10.0-rc-1, 16.10.2, 16.2.0-rc-1, 16.3.1, 16.4.0, 16.4.0-rc-1, 16.4.1, 16.4.2, 16.5.0, 16.5.0-rc-1, 16.6.0, 16.7.0, 16.7.1, 16.8.0, 16.8.0-rc-1, 16.9.0, 16.9.0-rc-1

Someone with bulk edit can assign all the above at once. I know it's weird to edit one issue using bulk edit, but it beats selecting those one at a time.