[feat] Support prompt embedding caching for diffusion model (#2962)

Signed-off-by: knlnguyen1802 <knlnguyen1802@gmail.com>
Co-authored-by: Samit <285365963@qq.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/diffusion/test_diffusion_model_runner.py

@@ -52,6 +52,7 @@ def _make_runner(cache_backend, cache_backend_name: str, enable_cache_dit_summar
     runner.pipeline = _DummyPipeline(output=SimpleNamespace(output="ok"))
     runner.cache_backend = cache_backend
     runner.offload_backend = None
+    runner.prompt_embed_cache = None
     runner.od_config = SimpleNamespace(
         cache_backend=cache_backend_name,
         enable_cache_dit_summary=enable_cache_dit_summary,