Wrt: meta-pipewire/recipes-multimedia/pipewire/pipewire.conf

This is a (distro-specific) configuration. In a later changeset we should split this from the (binary) package of pipewire.

a) it makes the pipewire recipe upstreamable

b) a virtual/pipewire-config allows to deploy a different config 'as-needed' with a PREFERRED_PROVIDER variable.

c) the binary package for pipewire does not ship configuration

Note: we'll do this in a follow-up after RC1.

TLDR:

• pipewire_git.bb gets a DEPENDS += "virtual/pipewire-config"
• remove the config file deployment from pipewire_git.bb
• a new pipewire-config-agl.bb deploys the pipewire.conf and PROVIDES += "virtual/pipewire-config"