Make init process create PDX sockets for services

To help us control the creation of PDX sockets and properly labeling
them for SELinux, let the init process create sockets for us based on
the settings specified in .rc files for service processes.

For (test) services that are meant to be started manually from command
line (e.g. test services), keep the old functionality as an option so
that UDS endpoint can be created in a way that it automatically creates
the socket in the service itself.

Bug: 35220925
Test: `m -j32` succeeds. Ran sailfish in VR mode and made sure all the
      services (surfaceflinger, performanced, sensord, bufferhub).
      `m -j32 checkbuild` succeeds as well.

Change-Id: Ief733b41b534cea19b1bea31de76b06051aa50ab