Can we move the `cabal install <library>` warning to the start instead of the end and/or just refuse to do it without some option?

Currently you get a dubiously installed library followed by a warning that says you probably didn't want to do that and suggests `--lib`. IMO both are wrong: we should just not do it, and `--lib` shouldn't be suggested, instead point users to the manual which should mention `--lib`, warn about the consequences, and very strongly recommend using it with `--package-env`.

(This said, there are a _lot_ of users on Discord who are convinced that automatic package management is a Bad Thing and we should immediately dump it and go back to sandboxes as the only proper way to ever do package management. I personally think Python has warped people even worse than is immediately obvious.)