ci: Always use CI_PROJECT_NAMESPACE instead of CI_PROJECT_PATH

And always check it first.

Cleanup for consistency.

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6566>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 41f1eb9..076e64e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -48,10 +48,10 @@
     - if: &is-for-marge '$GITLAB_USER_LOGIN == "marge-bot"'
       when: never
     # Forked project branch
-    - if: &is-forked-branch '$CI_PROJECT_PATH != "mesa/mesa" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME != $CI_COMMIT_REF_NAME'
+    - if: &is-forked-branch '$CI_PROJECT_NAMESPACE != "mesa" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME != $CI_COMMIT_REF_NAME'
       when: manual
     # Forked project branch / pre-merge pipeline
-    - if: &is-forked-branch-or-pre-merge '$CI_PROJECT_PATH != "mesa/mesa" || $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_COMMIT_REF_NAME'
+    - if: &is-forked-branch-or-pre-merge '$CI_PROJECT_NAMESPACE != "mesa" || $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_COMMIT_REF_NAME'
       when: manual
     # Pipeline runs for the master branch of the main project
     - if: &is-main-master '$CI_PROJECT_NAMESPACE == "mesa" && $CI_COMMIT_REF_NAME == "master"'
@@ -60,7 +60,7 @@
     - if: &is-post-merge '$CI_PROJECT_NAMESPACE == "mesa" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME != $CI_COMMIT_REF_NAME'
       when: on_success
     # Post-merge pipeline, not for Marge Bot
-    - if: &is-post-merge-not-for-marge '$GITLAB_USER_LOGIN != "marge-bot" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME != $CI_COMMIT_REF_NAME && $CI_PROJECT_PATH == "mesa/mesa"'
+    - if: &is-post-merge-not-for-marge '$CI_PROJECT_NAMESPACE == "mesa" && $GITLAB_USER_LOGIN != "marge-bot" && $CI_MERGE_REQUEST_SOURCE_BRANCH_NAME != $CI_COMMIT_REF_NAME'
       when: on_success
     # Pre-merge pipeline
     - if: &is-pre-merge '$CI_MERGE_REQUEST_SOURCE_BRANCH_NAME == $CI_COMMIT_REF_NAME'