Inherit marketing campaing opportunity abstract models in right order

Abstract models should be always the last in inheritance because
they are object when optional dependencies are not activated
PoolMeta shold be added because all classes in the pool must inherit from it

Closes #12375

modules/marketing_campaign/sale_opportunity_reporting.py

@@ -66,7 +66,7 @@ class Context(MarketingCampaignMixin, metaclass=PoolMeta):
         return default
 
 
-class MarketingContext(BaseContext):
+class MarketingContext(BaseContext, metaclass=PoolMeta):
     "Sale Opportunity Reporting Context"
     __name__ = 'sale.opportunity.reporting.marketing.context'
 
@@ -78,7 +78,7 @@ class MarketingContext(BaseContext):
         lazy_gettext('marketing_campaign.msg_marketing_source'))
 
 
-class Marketing(MarketingCampaignMixin, Abstract, ModelView):
+class Marketing(MarketingCampaignMixin, ModelView, Abstract):
     "Sale Opportunity Reporting per Marketing"
     __name__ = 'sale.opportunity.reporting.marketing'