Created by: LiuChiachi

PR types

New features

PR changes

APIs

Describe

This PR solved 3 TODOs in last PR #25894 about hapi.model._save_inference_model by using new features of dy2stat #25960 in 2.0-beta API.

1. Make it Unnecessary to run model before calling _save_inference_model for users in dygraph.
2. Save correct shape of input, now the interface stores the shape that the user sent to the inputs of the model in running.
3. Make it Unnecessary to add @paddle.jit.to_static for users in dynamic mode.