Delegate model adapter credential to runtime to download model adapters

[Jeffwan]

🚀 Feature Description and Motivation

Model Adapter could come from different object storage. We can not assume the base model can only consume models from same object store.

In order to achieve the flexible setting, we should consider to assume the roles and allocate short term tokens to runtime to download the model

part of #1818

Use Case

for model adapter downloading

Proposed Solution

No response