ada: Factor out tag assignments from type in expander
They are performed in a few different places during expansion.
gcc/ada/
* exp_util.ads (Make_Tag_Assignment_From_Type): Declare.
* exp_util.adb (Make_Tag_Assignment_From_Type): New function.
* exp_aggr.adb (Build_Record_Aggr_Code): Call the above function.
(Initialize_Simple_Component): Likewise.
* exp_ch3.adb (Build_Record_Init_Proc.Build_Assignment): Likewise.
(Build_Record_Init_Proc.Build_Init_Procedure ): Likewise.
(Make_Tag_Assignment): Likewise. Rename local variable and call
Unqualify to go through qualified expressions.
* exp_ch4.adb (Expand_Allocator_Expression): Likewise.