API module manager and help rewrite

API module manager and help rewrite

This is a non-versioned part of the larger patch #41014
https://gerrit.wikimedia.org/r/#/c/41014
It will allow help subsystem optimization (merging paraminfo and help),
path towards per-module or per-system versioning, removal of the
manually maintained generator lists.

Changes:
* ApiModuleManager now handles all submodules (actions,props,lists) and instantiation
* ApiModuleManager maintains a cache of all instantiated modules
* Query stores prop/list/meta as submodules
* action=help suports generalized submodules (modules=query+value), querymodules obsolete

Change-Id: Ie2dee41e44a29cd5d5935eeaa5240b708d95a8f0