Use ObjectFactory to create API modules

Use ObjectFactory to create API modules

This will allow constructing API modules that need services.

This overhauls some of the internals of the ApiModuleManager,
but the public interface remains unchanged.
The $class parameter of addModule, (now called $spec)
also allows passing an array with the spec of the module.
Note that this spec requires the attribute 'class' to be present,
even when 'factory' is specified. This is the same as before,
where $class was always required.

In a perfect DI world ObjectFactory would be injected into
ApiMain::__construct and ApiMain would pass that to its instance
of ApiModuleManager, but that is currently not possible, so for now
it is injected in ApiModuleManager by having ApiMain::__construct
call the service locator.

Bug: T222388
Change-Id: Iee04afc27283547dd68d6db93f44ac2e0ebf1258