PRs ready for review _

###### Description of changes This change adds two packages: mgmt and nex. Th…e latter is a build dependency for the former. Unfortunately both do not have stable releases, thus each tracks the tip of their respective upstream branches. Go module pseudo versions are used. mgmt: Next generation distributed, event-driven, parallel config management! nex: Lexer for Go Fixes #98458 purpleidea/mgmt#610 ###### Things done - Built on platform(s) - [x] x86_64-linux - [ ] aarch64-linux - [ ] x86_64-darwin - [ ] aarch64-darwin - [ ] For non-Linux: Is `sandbox = true` set in `nix.conf`? (See [Nix manual](https://nixos.org/manual/nix/stable/command-ref/conf-file.html)) - [x] Tested, as applicable: - [NixOS test(s)](https://nixos.org/manual/nixos/unstable/index.html#sec-nixos-tests) (look inside [nixos/tests](https://github.com/NixOS/nixpkgs/blob/master/nixos/tests)) - and/or [package tests](https://nixos.org/manual/nixpkgs/unstable/#sec-package-tests) - or, for functions and "core" functionality, tests in [lib/tests](https://github.com/NixOS/nixpkgs/blob/master/lib/tests) or [pkgs/test](https://github.com/NixOS/nixpkgs/blob/master/pkgs/test) - made sure NixOS tests are [linked](https://nixos.org/manual/nixpkgs/unstable/#ssec-nixos-tests-linking) to the relevant packages - [x] Tested compilation of all packages that depend on this change using `nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD"`. Note: all changes have to be committed, also see [nixpkgs-review usage](https://github.com/Mic92/nixpkgs-review#usage) - [x] Tested basic functionality of all binary files (usually in `./result/bin/`) - [22.11 Release Notes (or backporting 22.05 Release notes)](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md#generating-2211-release-notes) - [ ] (Package updates) Added a release notes entry if the change is major or breaking - [ ] (Module updates) Added a release notes entry if the change is significant - [ ] (Module addition) Added a release notes entry if adding a new NixOS module - [ ] (Release notes changes) Ran `nixos/doc/manual/md-to-db.sh` to update generated release notes - [x] Fits [CONTRIBUTING.md](https://github.com/NixOS/nixpkgs/blob/master/CONTRIBUTING.md).

https://github.com/NixOS/nixpkgs/pull/199592
https://github.com/NixOS/nixpkgs/pull/200065
https://github.com/NixOS/nixpkgs/pull/200139
https://github.com/NixOS/nixpkgs/pull/200148
https://github.com/NixOS/nixpkgs/pull/200157
https://github.com/NixOS/nixpkgs/pull/200179
https://github.com/NixOS/nixpkgs/pull/202978
https://github.com/NixOS/nixpkgs/pull/202982
https://github.com/NixOS/nixpkgs/pull/203012
https://github.com/NixOS/nixpkgs/pull/203017
https://github.com/NixOS/nixpkgs/pull/203020