event: Inject 'd' into event handlers

To quote Chris Larson:

"""
e.data.getVar() gets a bit old in a large event handler, and it means a simple handler has to be modified if switching between an event handler (e.g. RecipeParsed) and anonymous python. I think it would make sense to restore the 'd' convention here to align with python elsewhere. It'd just be a convenience, d==e.data, to avoid the common pattern of setting it at the top of the event handler.
"""

I couldn't find a way to inject 'd' via locals/globals due to the use of a function parameter so this left __builtins__ as the only way I could find to make this work.

[YOCTO #7668]

index f755eb2..80e3796 100644
@@ -72,6 +72,7 @@ _eventfilter = None
 
 def execute_handler(name, handler, event, d):
     event.data = d
+    __builtins__['d'] = d
     try:
         ret = handler(event)
     except bb.parse.SkipRecipe:

@@ -87,6 +88,7 @@ def execute_handler(name, handler, event, d):
             logger.error("Execution of event handler '%s' failed (exit code %s)" % (name, exc.code))
     finally:
         del event.data
+        del __builtins__['d']
 
 def fire_class_handlers(event, d):
     if isinstance(event, logging.LogRecord):