[CI] Move JIT kernel tests + benchmarks to test/registered/jit; add in-package guard (#27644)

.github/workflows/pr-test.yml

@@ -388,7 +388,7 @@ jobs:
       caller_inputs: ${{ toJson(inputs) }}
       partitions: ${{ needs.check-changes.outputs.partitions }}
       run_timeout_minutes: '40'
-      extra_pytest_path: 'python/sglang/jit_kernel/tests/test_flash_attention_4.py'
+      extra_pytest_path: 'test/registered/jit/test_flash_attention_4.py'
     secrets: inherit
 
   call-multimodal-gen-tests: