[Ada] Ada2022: implementation of AI12-0212 : iterator specs in array aggregates

[Ada] Ada2022: implementation of AI12-0212 : iterator specs in array aggregates

gcc/ada/

	* sem_aggr.adb (Resolve_Array_Aggregate): Check the validity of
	an array aggregate all of whose components are iterated
	component associations.
	* exp_aggr.adb (Expand_Array_Aggregate,
	Two_Pass_Aggregate_Expansion): implement two-pass algorithm and
	replace original aggregate with resulting temporary, to ensure
	that a proper length check is performed if context is
	constrained. Use attributes Pos and Val to handle index types of
	any discrete type.