feat: allow any and all executors

[jayy-lmao]

Hey there @fbucek!

Feel free to toss this out / suggest changes. I was recently finding a need for this at work, and had to fork in order for it to fit the needs of our project.

There were a couple of major changes, happy to open a PR with any combination of them instead of this PR.

• 1. Removed eyre and rely on sqlx result types where possible -- Consuming libaries/binaries may not want to opt into the error library just to use this, whereas they are already using sqlx
• 2. Replaced Pool with Executor -- This allows you to use the insert with DB Transactions, which is sometimes desired behavior when working with insert/update.
• 3. Remove return of Insert -- Unfortunately this was necessary in order to allow transactions (in my case). Maybe there could be two inserts; one which returns data and one which does not
• 4. Added the ability to update -- I'm finding it useful but it may not be what people want 🤷

Like I said, was just trying to accelerate progress on a work project. If you want any of it I can spend a bit of my own time tidying it up / making any changes you want etc.

I've tested it my project and it has worked fine.

[fbucek]

Thanks for contribution.

1) Eyre can be removed from all the code. 2) Executor instead of pool is much better. 3) Unfortunatelly insert without return is not ok. But maybe adding another method insert_get::<Car> would be fine. 4) Update method is ok, I do not now whether it will be usefull but it is just a few lines so I would keep it.

I will look into in this week I hope.