[lldb/DWARF] Look for complete array element definitions in other modules

This applies the same logic we have for incomplete class bases and
members to array element types.

lldb/test/API/functionalities/limit-debug-info/main.cpp

@@ -22,4 +22,7 @@ struct TwoAsMember {
   int member = 47;
 } two_as_member;
 
+array::One array_of_one[3];
+array::Two array_of_two[3];
+
 int main() { return 0; }