Remove most of the metaprogramming in node.h in favor of listing all the members in the typed node structs. (#3310)

Split `node.h` into separate files for ID types (`id.h`) and for typed
nodes (`typed_nodes.h`). The per-node-kind data is now specified as part
of declaring the typed nodes, and is removed from the node kinds
x-macros, which now simply enumerate the node kinds.

toolchain/check/handle_array.cpp

@@ -42,9 +42,9 @@ auto HandleArrayExpression(Context& context, Parse::Node parse_node) -> bool {
     if (bound_value.getActiveBits() <= 64) {
       context.AddNodeAndPush(
           parse_node,
-          SemIR::ArrayType(
+          SemIR::ArrayType{
               parse_node, SemIR::TypeId::TypeType, bound_node_id,
-              ExpressionAsType(context, parse_node, element_type_node_id)));
+              ExpressionAsType(context, parse_node, element_type_node_id)});
       return true;
     }
   }