Deprecate the batch XML namespace

[fmbenhassine]

Following the deprecation of the mvc namespace in Spring Framework 7, we are intending to deprecate the batch XML namespace support (in favor of Java configuration) which has been causing several issues like #4533, #1158 and others.

There is no plan to remove the support for XML configuration style in any minor release of v6, but the XSD will not be updated to align with the Java configuration from v6 onwards.