Part of #27065
This reduces the usage of `db.DefaultContext`. I think I've got enough
files for the first PR. When this is merged, I will continue working on
this.
Considering how many files this PR affect, I hope it won't take to long
to merge, so I don't end up in the merge conflict hell.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Lunny Xiao