ci: extract cuda stage actions + runner_config mapping (#25138)

Co-authored-by: Alison Shao <54658187+alisonshao@users.noreply.github.com>

scripts/ci/runner_configs.py

@@ -0,0 +1,27 @@
+"""Emit a runner_config's setup details (install / artifact_version /
+install_timeout) in $GITHUB_OUTPUT format. Reads scripts/ci/runner_configs.yml.
+Called by .github/workflows/_pr-test-stage.yml.
+"""
+
+import os
+import sys
+
+import yaml
+
+_YAML_PATH = os.path.join(os.path.dirname(__file__), "runner_configs.yml")
+
+
+def load() -> dict:
+    with open(_YAML_PATH) as f:
+        return yaml.safe_load(f)["runner_configs"]
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        sys.exit("usage: runner_configs.py <runner_config>")
+    rc = sys.argv[1]
+    config = load().get(rc)
+    if config is None:
+        sys.exit(f"unknown runner_config: {rc!r}")
+    for key, value in config.items():
+        print(f"{key}={value}")