CI: Reduce max number of tests to 8/4

CI is hitting various limits after we started out with 32. In
particular, the default runners hit 90s test timeouts.

And the asan runner runs into max threads limits, so reduce that one to
4 tests max.

.gitlab-ci.yml

@@ -26,7 +26,7 @@ variables:
   BACKEND_FLAGS: "-Dx11-backend=true -Dwayland-backend=true -Dbroadway-backend=true"
   FEATURE_FLAGS: "-Dvulkan=enabled -Dcloudproviders=enabled -Dbuild-testsuite=true -Dintrospection=enabled"
   MESON_TEST_TIMEOUT_MULTIPLIER: 3
-  MESON_TEST_MAX_PROCESSES: 32
+  MESON_TEST_MAX_PROCESSES: 8
   FEDORA_IMAGE: "registry.gitlab.gnome.org/gnome/gtk/fedora:v52"
 
 workflow:
@@ -420,6 +420,7 @@ asan-build:
   stage: analysis
   needs: []
   variables:
+    MESON_TEST_MAX_PROCESSES: 4
   script:
     - export PATH="$HOME/.local/bin:$PATH"
     - CC=clang meson setup