Tasks inside the content of other macros are not assigned an ID

[trrenty]

Steps to reproduce:

1. Add a macro that supports xwiki syntax. e.g. {{info}}
2. Add inside the info macro a task macro
3. Save and view the page
   Expected:
   The rendered task has a link to its associated page with the id as a label.
   Actual:
   The task has no link

This happens because the the id and task reference are created using a DocumentUpdating listener. This listener checks the XDOM of the document and creates a document for the task and puts that reference in the parameters of the macro. The issue is that it only checks the content of the page, not also the content of other macros.

To fix this, we need to recursively check the content of the macros that support xwiki syntax 2.1 and process the tasks inside them.