[Aggregate]XML declaration in CDATA part is removed by aggregation

[Hooghof]

An aggregation of a message body that contains a CDATA section containing an xml declaration proceeds differently than in Camel2. An xml declaration must first be added to the body so that the aggregation component understands that it is an xml body.

On acceptance and on development there are identical testcases in the flow called aggregateXmlCdata (tenant Regression Tests). The test contains 3 routes:

1. Without xml declaration and without Content-Type text/xml
2. Without xml declaration but with Content-Type text/xml
3. With xml declaration

On acceptance, the 3 test cases have the same output.
On development, only test case 3 gives the expected output.

https://dovetailworld.atlassian.net/browse/DOV-2173