Implement event information for workflowTaskReassigned and workflowTaskDelegated

In the context of the events workflowTaskReassigned and workflowTaskDelegated, no workflow context variables can be fetched as documented.

How to reproduce:

• Start a sample mail server and configure Nuxeo 9.10 to use it
• Take the sample project and deploy it on a Nuxeo 9.10 instance and login in JSF as Administrator
• Create a Note document
• Start the workflow DelegateTemplateBis on the Note document
• You are given the first task => no mail flows, as configured for the first task
• Approve the first task => the mail that the second task has been assigned flows in
• In the Workflow tab of the document, reassign the task => exception happens
• Still in the Workflow tab, delegate the task => exception happens

What to expect:
The 2 custom pieces of mail for task reassignment and delegation should work seamlessly as done in the case of the task assignment

Analysis
A bit of inquiry in the sample project will show that task assignment and task reassignment use the same subject and body. In the task assignment case, it works great; in the task reassignment case, it chokes badly.
If changing the subject of the task reassignment to not use any workflow related variable, you get NO exception but the body of the mail is incomplete (missing workflow and task related information)