Postico 2: Creating one-off queries is clumsy

Feedback from @9mm (originally posted [here](https://github.com/jakob/Postico/issues/72#issuecomment-591001917))

> I don't know if this is a good spot to comment on Postico 2 as well, but the one thing keeping me from using it is it's no longer able to do an SQL query in one click. That's mostly the whole point of why I use Postico for many production servers.
>
> Now, many clicks are involved and it just feels very clunky/clumsy to do a single query, and that it just saves every single one. I rarely am wanting to save what I'm doing. Maybe there can be a "Quick SQL" section above the one where it automatically stores it or something...
>

The issue names Postico 2's SQL-query creation flow and suggests a “Quick SQL” section; no source files or tests are identified. Start by locating that flow and the automatic query-saving behavior. Done means a one-off query can be opened with fewer clicks without being saved by default, while existing saved queries remain usable.

Written by the indexing model from the issue text.