ci/angle: condense angle variables in one job

Use .test-angle as a full-featured job to be extended to enable angle
usage in the job. Right now, it comes with USE_ANGLE=1 flag and the
respective structural tag.

Signed-off-by: Guilherme Gallo <guilherme.gallo@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33421>

.gitlab-ci/test/gitlab-ci.yml

@@ -182,6 +182,12 @@ yaml-toml-shell-py-test:
   variables:
     ANGLE_TAG: ${CONDITIONAL_BUILD_ANGLE_TAG}
 
+.test-angle:
+  extends:
+    - .tag-check-angle
+  variables:
+    USE_ANGLE: 1
+
 .b2c-vkd3d-proton-test:
   variables:
     HWCI_TEST_SCRIPT: install/vkd3d-runner.sh