flow: 0.49.1 -> 0.54.0

[frontsideair]

Motivation for this change

New upstream release

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

[mention-bot]

@frontsideair, thanks for your PR! By analyzing the history of the files in this pull request, we identified @puffnfresh, @msteen and @globin to be potential reviewers.

[Mic92]

Thanks!