ada: Improved legality checking for deep delta aggregates.

ada: Improved legality checking for deep delta aggregates.

Enforce deep delta legality rules about nonoverlapping choices. For example,
do not allow both Aaa.Bbb and Aaa.Bbb.Ccc as choices in one delta aggregate.
One special case impacts "regular" Ada2022 delta aggregates - the rule
preventing a record component from occurring twice as a choice in a delta
aggregate was previously not being enforced.

gcc/ada/ChangeLog:

	* sem_aggr.adb (Resolve_Delta_Aggregate): The rule about
	discriminant dependent component references in choices applies to
	both array and record delta aggregates, so check for violations in
	Resolve_Delta_Aggregate. Call a new procedure,
	Check_For_Bad_Dd_Component_Choice, for each choice.
	(Resolve_Delta_Record_Aggregate): Call a new procedure,
	Check_For_Bad_Overlap, for each pair of choices.