Refactor `flake.nix`

[SchahinRohani]

Description

Refactoring the flake into tools for better accessability.

Depends on this PR #1268.

How Has This Been Tested?

The command nix flake checkand nix flake show are throwing errors, so i need to refactor the flake first to be able to test it properly.

Checklist

• [ ] Updated documentation if needed
• [ ] Tests added/amended
• [ ] bazel test //... passes locally
• [ ] PR is contained in a single commit, using git amend see some docs

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This change is