ISPN-4867 Single event marshaller support more clearly defined in API

* Based on Dan's feedback, Hot Rod server API made it look as if you
could pass a per-factory marshaller but that's not really the case.
A single event marshaller is currently supported.
ISPN-4675 Missing server configuration for remote executor thread pool

Add server configuration for the remote command executor and the total order executor.
ISPN-3938 AdvancedAsyncCacheLoader.process() concurrency issues

Simplify ExecutorAllCompletionService to track the tasks itself instead of
using an ExecutorCompletionService.