Allow seeing reason of version resolution failure

[Nicd]

In #3002 the reason for version resolution failures was changed to a more simplified version. Example:

➜  aurinko git:(trunk) ✗ gleam deps download
  Resolving versions
error: Dependency resolution failed

An error occurred while determining what dependency packages and
versions should be downloaded.
The error from the version resolver library was:

Unable to find compatible versions for the version constraints in your
gleam.toml. The conflicting packages are:

- aurinko
- mist
- wisp

When you have many packages that have many of their own dependencies, finding out the reason for the failure is not trivial even if it tells you which packages are involved. It would be useful to have a flag --detailed-errors or something like that to allow seeing the admittedly complicated error message that originally existed. I feel that it would be better than nothing. Currently I'm going through Hex.pm, trying to deduce the dependency ranges in my head, but it's difficult as I don't even know which dependency the failure is about.