Fix bugs related to task_includes and dep chain inheritance

* Fix the way task_include fields were created and copied
* Have blocks get_dep_chain() look at task_include's blocks for proper
  dep chain inheritance
* Fix the way task_include fields are copied to prevent a recursive
  degradation

Fixes #14460

lib/ansible/playbook/block.py

@@ -153,6 +153,8 @@ class Block(Base, Become, Conditional, Taggable):
         if self._dep_chain is None:
             if self._parent_block:
                 return self._parent_block.get_dep_chain()
+            elif self._task_include:
+                return self._task_include._block.get_dep_chain()
             else:
                 return None
         else: