[ISSUE #726] feat: replace fmt to rlog

[yuanmoon]

What is the purpose of the change

#726

Brief changelog

Replace fmt to rlog

Verifying this change

XXXX

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[yuanmoon]

It seems that the failure of Travis CI is caused by this bug(#757).
And here is the bug fix pr(#758).
So grateful if someone can help to confirm this.

[wenfengwang]

@yuanmoon Hi, the directory of examples is the demo for users for their business, so, we can not use rlog in these files

[yuanmoon]

@wenfengwang
Thanks for review. I just follow your advice to roll back code. You can check again and please let me know if there are still places that need to be modified.