Adding targets from the debug screen as checkable properties in predicates

Adding the targets from the debug screen (Targeted Block, Targeted Fluid, and Targeted Entity) as checkable properties in predicates.

I've had this idea in my head for a while. After considering all the options, I think the most fitting place to check for these targets is with predicates. I'm open to ideas on how to improve this suggestion. I'm happy to expand on the suggestion if it needs more information. 

This is different than the targeted_entity condition that can be checked under entity_properties, as that only checks for the entity that has targeted for attacks.  

I have two suggestions for implementation:

• Either the condition would be checked under the player properties in the entity_properties condition, named targeted_block, targeted_fluid, and targeted_entity 
• or implemented under a new condition named target_check that would allow children named entity_properties, fluid_properties, or block_properties. 

Why implement this idea?

Predicates are used to check for conditions in advancements and loot tables. All three of the targets on the debug screen are relevant to custom advancements and loot tables. Looking at a block, entity, or fluid ought to be considered a player action just as much as walking through, breaking, placing, or killing qualify as conditions for advancements. Consider a custom data pack that uses advancements to reward the player for finding all of the mobs in the game. Currently, this is not easily done, but it could be.