[Epic] Most Expensive Queries

This is an epic to track our most expensive SQL Queries as measured in our dogfood system and work to improve, either by making them faster or less frequent.

It also tracks general improvements that will help us track, diagnose, and remediate future expensive queries.

* [x] coder/internal#715
* [x] coder/internal#716
* [x] coder/internal#717
* [x] coder/internal#718
* [x] coder/internal#719
* [x] coder/internal#720
* [x] coder/internal#721
* [x] coder/internal#722
* [x] https://github.com/coder/coder/issues/17689
* [x] coder/internal#724
* [x] coder/internal#725
* [x] coder/internal#726
* [x] coder/internal#727
* [x] coder/internal#728
* [x] coder/dogfood#166
* [x] https://github.com/coder/coder/issues/20817