MM-63285: Add property field methods to plugin API (#31035)

Co-authored-by: Claude <noreply@anthropic.com>

server/public/plugin/client_rpc.go

@@ -168,6 +168,7 @@ func init() {
 	gob.Register(&model.AutocompleteStaticListArg{})
 	gob.Register(&model.AutocompleteTextArg{})
 	gob.Register(&model.PreviewPost{})
+	gob.Register(model.PropertyOptions[*model.PluginPropertyOption]{})
 }
 
 // These enforce compile time checks to make sure types implement the interface