move package-, version update scripts to flake apps

[leona-ya]

This is to support the update-nixpkgs workflow without a devenv shell.

@flyingcircusio/release-managers

Release process

• Created changelog entry using ./changelog.sh
  • No: this is a internal follow up to the unreleased Add update-nixpkgs cleanup action #1186.

PR release workflow (internal)

• PR has internal ticket
• internal issue ID (PL-…) part of branch name
• internal issue ID mentioned in PR description text
• ticket is on Platform agile board
• ticket state set to Pull request ready
• if ticket is more urgent than within the next few days, directly contact a member of the Platform team

Design notes

• Provide a feature toggle if the change might need to be adjusted/reverted quickly depending on context. Consider whether the default should be on or off. Example: rate limiting.
• All customer-facing features and (NixOS) options need to be discoverable from documentation. Add or update relevant documentation such that hosted and guided customers can understand it as well.

Security implications

• Security requirements defined? (WHERE)
  • works
• Security requirements tested? (EVIDENCE)
  • tested locally with nix run .#{buildVersionsJson, buildPackageVersionsJson}