Ada: Fix packed boolean array with Default_Component_Value aspect

Ada: Fix packed boolean array with Default_Component_Value aspect

Putting the Default_Component_Value aspect on a bit-packed array type has
never worked, so this plugs the loophole.  For the sake of consistency,
the recent fix for PR ada/68179 is adjusted to use Has_Default_Aspect too.

gcc/ada/
	PR ada/68179
	PR ada/123589
	* exp_ch3.adb (Expand_Freeze_Array_Type): Build an initialization
	procedure for a bit-packed array type if Has_Default_Aspect is set
	on the base type, but make sure not to build it twice.  Also test
	Has_Default_Aspect for a type derived from String.

gcc/testsuite/
	* gnat.dg/component_value2.adb: New test.

Co-authored-by: Lisa Felidae <lisa@felidae.bam.moe>