Sbt credentials scoping to build rather than projects.

[zarthross]

Description

In Sbt (prior to 2.0) a sbt key not scoped to ThisBuild will always be at the project level, rather than at the build level.
In order to do some things, like use a private repository configured by sbt with sbt-scalafix, we need the credentials scope to the build, otherwise the credentials show as non-existant.

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC

@kubukoz

[zarthross]

@rycee Can you give this a look please? 🥺