In Model Runner, is_encoder_decoder is exacted from model_config to determin whether vllm is running for enc-dec models. Obtaining this status requires a long call stack, and the CPU overhead is high. So this PR cache this status in __init__ of ModelInputForNPUBuilder. Signed-off-by: hw_whx <wanghexiang7@huawei.com> Co-authored-by: hw_whx <wanghexiang7@huawei.com>