Add a slow flag to commands with heavy disk IO

[PragmaTwice]

Search before asking

• [X] I had searched in the issues and found no similar issues.

Motivation

We can add a new command flag e.g. slow and apply it to all commands that can lead to heavy disk IO (rocksdb read/write).

Solution

No response

Are you willing to submit a PR?

• [ ] I'm willing to submit a PR!