[torch.compile] rework compile control with piecewise cudagraph (#9715)

Signed-off-by: youkaichao <youkaichao@gmail.com>

.buildkite/test-pipeline.yaml

@@ -229,6 +229,9 @@ steps:
   - tests/compile
   commands:
   - pytest -v -s compile/test_basic_correctness.py
+  # these tests need to be separated, cannot combine
+  - pytest -v -s compile/piecewise/test_simple.py
+  - pytest -v -s compile/piecewise/test_toy_llama.py
 
 - label: "PyTorch Fullgraph Test" # 18min
   source_file_dependencies: