Deprecate src/sage/misc/db.py

<div id="comment:0"></div>

Yet another essentially unused module.

Depends on #17460

Component: **misc**

Author: **Jeroen Demeyer**

Branch/Commit: **[`fc4d2e4`](https://github.com/sagemath/sagetrac-mirror/commit/fc4d2e40cd173ba4038c0474867e207a0edfe1c0)**

Reviewer: **Vincent Delecroix**

_Issue created by migration from https://trac.sagemath.org/ticket/17653_

