Migrate some function properties into a shared_ptr

The idea is that we can return the shared pointer directly, avoiding
lots of annoying little getter functions that each need to take locks.
It also helps to pull together the data structures used to initialize
functions versus store them.

src/builtin_function.cpp

@@ -249,23 +249,20 @@ int builtin_function(parser_t &parser, io_streams_t &streams, const wcstring_lis
     if (!opts.description.empty()) d.description = opts.description;
     // d.description = opts.description;
     d.events.swap(opts.events);
-    d.shadow_scope = opts.shadow_scope;
-    d.named_arguments.swap(opts.named_arguments);
-    d.inherit_vars.swap(opts.inherit_vars);
+    d.props.shadow_scope = opts.shadow_scope;
+    d.props.named_arguments = std::move(opts.named_arguments);
+    d.inherit_vars = std::move(opts.inherit_vars);
 
     for (size_t i = 0; i < d.events.size(); i++) {
         event_t &e = d.events.at(i);
         e.function_name = d.name;
     }
 
-    d.parsed_source = source;
-    d.body_node = body;
-    function_add(d, parser);
+    d.props.parsed_source = source;
+    d.props.body_node = body;
+    function_add(std::move(d), parser);
 
     // Handle wrap targets by creating the appropriate completions.
-    for (size_t w = 0; w < opts.wrap_targets.size(); w++) {
-        complete_add_wrapper(function_name, opts.wrap_targets.at(w));
-    }
-
+    for (const wcstring &wt : opts.wrap_targets) complete_add_wrapper(function_name, wt);
     return STATUS_CMD_OK;
 }