firefox: organize tests by submodule

[kira-bruneau]

Description

Split off from #5697, organizes firefox tests by submodule.

This is intended to match directory structure setup for the new search submodule.

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

@rycee @brckd

[brckd]

Thank you! This doesn't seem to create merge conflicts as of yet.

Just note that firefox/firefox.nix was named like that so that other derivatives could be added to e.g. firefox/librewolf.nix. Changing it to firefox/default.nix suggests to add tests for other derivatives to e.g. librewolf/default.nix. I'm indifferent to this change.

[kira-bruneau]

Oh ok sorry! I didn't realize that was a recent change. I just noticed it seemed out of place compared to all the other tests. I'll change it back!

[kira-bruneau]

I tried rebasing in fe98bae to fix the macos-latest tests, but now ubuntu-latest is failing for an unrelated reason: NixOS/nixpkgs#345965.

I'll try again once that's been resolved.

[teto]

I am oblivious to the change but firefox maintainer approves so lets' merge