ExternalContextFactory cuts context from deployment context/requires dependency on module

WFLY-2777 changed CCL for context creation(if module is set in external context factory). This essentially cuts context from deployment classes during creation time. This can cause problems when external-context-factory.module classes (ObjectFactories, etc) require deployment classes to be visible from classloader which created context( external-context.module ) and are not found.

Steps to reproduce:
1. define isolated module IM ( with classloader IM_CL )
2. create external-context-factory with module set to IM
3. create some deployment with interface, for which proxies should be looked up via external-context ( with classloader D_CL ) - deployment has no dependency on IM, since it may contain legacy classes or unwanted dependencies
4. lookup and invoke proxy

Now what will happen is during deployment external-context will be spawned just fine. However, the runtime outcome wont be pleasing.
Case 1: application and custom context dont do CCL magic

• invocation happen in deployment CCL, hence IM_CL classes are not visible and no classes required for deserialization can be loaded, this will fail ( return javax.naming.Reference instance, since ObjectFactory from IM_CL cant be found )

Case 2: application or custom context switch CCL to IM_CL for lookup

• CCL is set to IM_CL, ObjectFactory can be found, but D_CL classes cant, hence some naming error probably

Neither of above will work, unless IM_CL and D_CL have some sort of dependency on each other, which just makes module CL configured in external-context-factory irrelevant, since D_CL will require dependency on IM_CL.

Workaround:
yes, store IM_CL in context wrapper and upon first invocation obtain CCL( hopefuly D_CL), create agregating CL and set it as CCL for each context invocation.

Possible fix:
1. pass D_CL and IM_CL as part of env to factory, to allow context/context-wrapper to do some magic
2. alter ExternalContextFactory and create agregating/delegating CL, which will just iterate over IM_CL and D_CL if present to load proper classes