ci: Only launch a single mocked D-Bus environment for all tests

This cuts away a lot of time wasted on spawning and tearing down D-Bus
daemons and mocked service for every test case.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2678>

.gitlab-ci.yml

@@ -367,8 +367,12 @@ build-without-native-backend-and-wayland@x86_64:
     - .test-mutter-base
   script:
     - glib-compile-schemas $GSETTINGS_SCHEMA_DIR
-    - dbus-run-session -- xvfb-run -a -s "$XVFB_SERVER_ARGS"
-        ./.gitlab-ci/run-meson.sh test -C build
+    - xvfb-run -a -s "$XVFB_SERVER_ARGS"
+        ./src/tests/meta-dbus-runner.py
+          --launch=wireplumber
+          meson test
+            -C build
+            --setup plain
             --no-suite 'mutter/kvm'
             --no-rebuild
             --timeout-multiplier 10
@@ -495,8 +499,10 @@ dist-mutter:
     - meson . build --werror --prefix /usr
         -Dbuildtype=debugoptimized
     - glib-compile-schemas $GSETTINGS_SCHEMA_DIR
-    - dbus-run-session -- xvfb-run -a -s "$XVFB_SERVER_ARGS"
-        ./.gitlab-ci/run-meson.sh dist -C build
+    - xvfb-run -a -s "$XVFB_SERVER_ARGS"
+        ./src/tests/meta-dbus-runner.py
+          --launch=wireplumber
+          meson dist -C build
   rules:
     - if: '$CI_PIPELINE_SOURCE == "merge_request_event"'
       changes:

.gitlab-ci/run-meson.sh

@@ -1,8 +0,0 @@
-#!/usr/bin/bash
-
-set -e
-
-wireplumber &
-sleep 1
-
-meson "$@"