Add toJSON methods (#1859)

* tojson things

* fix client

* ignore private properties

* remove extra property descriptors

* handle primitive flattening

* remove unused import

* add toJSON to collections

* reduce stateful props

* state

* allow custom prop names when flattening

* fix client

* fix build

* fix flatten docs

* remove guild.available, cleanup permissions, remove arbitrary id reduction

* fix util import

* add valueOf as needed, update member props

* fix incorrect merge

* update permissionoverwrites and permissions

remove serialization of permissions in PermissionOverwrites#toJSON.
change Permissions#toJSON to serialize permissions, by default excluding
admin checks.

* change Permissions#toJSON to return the primitive

* Permissions#toJSON explicitly return bitfield

src/client/Client.js

@@ -411,6 +411,15 @@ class Client extends BaseClient {
     );
   }
 
+  toJSON() {
+    return super.toJSON({
+      readyAt: false,
+      broadcasts: false,
+      pings: false,
+      presences: false,
+    });
+  }
+
   /**
    * Adds a ping to {@link Client#pings}.
    * @param {number} startTime Starting time of the ping