The proxy API is the one that we would like to expose for applications
and the other API is used internally when implementing modules or
factories.
The current pw_core object is really a context for all objects so
name it that way. It also makes it possible to rename pw_core_proxy
to pw_proxy later.
The pw_remote object is really a wrapper around the pw_core_proxy.
The events it emits are also available in the core proxy and are
generally awkward to use.
With some clever new pw_core_proxy_* methods and a pw_core_connect
to create the core_proxy, we can convert all code away from pw_remote.
This is a first step in this conversion, using the pw_remote behind
the scenes. It leaks into some places because it really needs to become
its own struct in a next step.
