wayland/weston-ini-conf: Add transmitter-output ini section

wayland/weston-ini-conf: Add transmitter-output ini section

And with it, build remoting plug-in when weston-waltham-remoting AGL
feature is set.

agl-compositor will use the remoting plug-in to create a remote output
so we need the remoting plug-in built as well as weston-remoting distro
feature.

v8 (mvlad): plain rebase to new folder structure, use AGL_FEATURES
instead of DISTRO_FEATURES
v7 (mvlad): plain rebase to new folder structure
v6 (jsmoeller): plain rebase to new folder structure

Bug-AGL: SPEC-3601

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>
Change-Id: Idf591e3f6954bdaafe917e5ceb93fde134dde8db
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/25454
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>