This is more in line with wayland and it allows us to create new
interfaces in modules without having to add anything to the type
enum. It also removes some lookups to map type_id to readable
name in debug.
Define a set of standard factory names and document what they
contain. This makes it possible to change the implementation by
mapping the factory-name to a different shared library.
Move the epoll functions to the system functions and make the loop
use those. Use simple mask for events instead of enum.
Add the used system api in pw_loop.
Add System API to spa_support and use it where possible.
Pass the system API used in the realtime loops in spa_support as
well and use this in the realtime paths.
Improve bootstrapping, load only the log and cpu interfaces because
those can/need to be shared between instances. Let the core load
the other interfaces.
Add keys to configure the System and Loop implementations used in
pw_loop.
Make a new API to hide some the implementation of eventfd, timerfd
and signalfd along with clock and read/write/ioctl/close functions.
We would like to have plugins use the abstractions so that we
can switch them to something else when needed.
