Server <modules> configuration with a single entry can break classloading

There's a bug in CacheContainerConfigurationBuilder introduced by changes for ISPN-7714. This happens only if we have a single module entry specified in the <modules> element of the cache container config and nothing in the 'module' attribute. In that case the module is used as if it was specified in the 'module' attribute. The classloader of the specified module is used as the global classloader of the cache container and this is almost always wrong. We should instead have an AggregatedClassloader of the classloaders of the user specified module/modules + the infinispan subsystem classloader (if no module attribute is present). If a 'module' attribute was specified then we should let that module be the designated classloader and do not use infinispan subsystem classloader as backup.