Remove shimo integration code on 16.7

What does this MR do and why?

Remove Shimo integration code.

Shimo has been disabled on CE/EE.

This MR deletes shimo-related codes and documents, and modifies shimo’s metric.

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Metric removal issue: #431438

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There was an old MR doing the same job before, because the code Base has changed a lot. Rebasing the old MR is not as good as recreating a new MR.

/cc JH EM @prajnamas

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