Fork with updates and new package

[drewburlingame]

Hi all. Given there's been no response from Sergey here or via LinkedIn, I've forked the repository and created a new package dbup-cli-2 with code from drewburlingame/dbup-cli. Please create new issues in that repo.

I've updated to support net8 and net9 and dropped all others for now.

I've also updated all the dependencies, including upgrading to dbup v6. It was only after updating all the code that I realized the dbup-postgresql is in beta. I'd rather not go back and update the code to use dbup 5 but will do if the beta is not completed soon.

I dropped CockroachDb support since the dbup packages for it are stale. Happy to add it back if the dbup packages are updated.

[AlexeyRaga]

Thanks for doing it @drewburlingame!
Will be switching to your fork early next year.