tests: Start pipewire and wireplumber for the native-unit test

So far, the tests relied on the host system to provide pipewire and
wireplumber. This seperates the tests from the host system which is
especially useful if the tests are run in a toolbox which has a
different pipewire installed than the host. It also should make it
harder to have a mismatch between the pipewire library and the pipewire
daemon.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3966>

src/tests/meson.build

@@ -370,6 +370,7 @@ test_cases += [
     'depends': [
       screen_cast_client,
     ],
+    'launch': [ 'pipewire', 'wireplumber' ],
   },
   {
     'name': 'pointer-constraints',
@@ -682,9 +683,19 @@ foreach test_case: test_cases
 
   test_depends = [ default_plugin ] + test_case.get('depends', [])
 
+  test_case_env = environment()
+  test_case_env_variables = test_env_variables
+  test_case_env_variables += {
+    'MUTTER_DBUS_RUNNER_LAUNCH': ','.join(test_case.get('launch', []))
+  }
+
+  foreach name, value: test_case_env_variables
+    test_case_env.set(name, value)
+  endforeach
+
   test(test_case['name'], test_executable,
     suite: ['core', 'mutter/' + test_case['suite']],
-    env: test_env,
+    env: test_case_env,
     depends: test_depends,
     is_parallel: false,
     timeout: 60,

src/tests/mutter_dbusrunner.py

@@ -298,6 +298,10 @@ def meta_run(klass):
     else:
         print('WARNING: Command or separator `--` not found', file=sys.stderr)
 
+    launch = os.getenv('MUTTER_DBUS_RUNNER_LAUNCH')
+    if launch:
+        args.launch.append(launch.split(','))
+
     if args.no_isolate_dirs:
         return meta_run_klass(klass, args, rest)