Unify the comment style.

[WenyXu]

I found the code bases have mixed two styles of comment. (But maybe it's not a big deal; some other projects I know also have this problem(e.g., arrow-rs)
https://github.com/apache/incubator-opendal/blob/0fe342a18cc1426523d2ded0e51ed99b9c629345/core/src/raw/ops.rs#L369-L395

Based on my experience, I personally prefer to use descriptive sentences, which follow the pingcap's style guide.

When used for description, comments should be descriptive rather than imperative.

Opens the file (Good)
Open the file (Bad)

https://pingcap.github.io/style-guide/rust/comments.html

[ankit-pn]

Hey I want to work on this issue, it would be great if anyone assign this to me!
Thanks

[Xuanwo]

Thanks for raising this but I don't have interest to review PRs that just polishes comment styles.

PRs for detailed behavior corrections are welcome. We can process them in separate issues instead.

[ankit-pn]

Ok thanks, you should close this issue.

[Xuanwo]

Ok thanks, you should close this issue.

Thank you for your interest in this project! You might want to check out these beginner-friendly issues: #3240 and #3803.

[ankit-pn]

thanks @Xuanwo . i checked these issues.

[Xuanwo]

Hi, @WenyXu, I'm closing this issue now. Welcome to leave comment if you have other ideas.