[curvefs]: change s3info

[Cyber-SiKu]

Is your feature request related to a problem? (你需要的功能是否与某个问题有关?)

At present, the backend s3 information stored in the curve file can only be specified when it is created, and cannot be changed later. But this will cause a problem: once the user's ak and sk are leaked, the fs becomes unavailable after changing the ak and sk.

At this time, the client's s3 information is also unavailable, and the client needs to be notified.

Describe the solution you'd like (描述你期望的解决方法)

I hope to add an interface and use tools to modify the information of s3 (ak, sk, bucket, endpoint).

Describe alternatives you've considered (描述你想到的折衷方案)

Additional context/screenshots (更多上下文/截图)

[harshitcodes22]

Assign me this please

[Cyber-SiKu]

Assign me this please

done

[Cyber-SiKu]

This is the pr that supports multi-s3 before, you can make a reference
#1132

[Cyber-SiKu]

@harshitcodes22
If you find it difficult now, you can take three steps (three PRs are enough):

1. Modify s3info in fsinfo on the mds side
2. After the mds is modified, notify the metaserver and update the s3adaptor
3. Notify the client after modification and update s3adaptor

[ken90242]

I am a software engineer at a tech company, working on the company's product business logic. I am interested in C++ and distributed systems.

I chose this topic because I previously worked on several issues for CurveFS, and I want to learn more about Curve design and implementation details.

[zztaki]

If this problem is not completed when the deadline is over or this friend gives up, please let me try :)