lomiri: init basic development stuff

[OPNA2608]

Description of changes

Working towards #99090, in more digestible steps than last time. This one is abit bigger, but the followups can be done more or less package-by-package with all of these present.

• create a maintainers team & package scope for Lomiri
  • if anyone wishes to join, add yourself and/or let me know 🙂
• init Lomiri-belonging things
  • cmake-extras: A set of CMake modules commonly used by Lomiri packages
  • lomiri-api: An API for integrating with the Lomiri shell
  • gmenuharness: A library to test GLib GMenuModels
• init some non-Lomiri things that are commonly used to drive tests
  • libqtdbustest: Library to test D-Bus interactions with Qt
  • libqtdbusmock: Library to mock D-Bus interactions with Qt
  • dbus-test-runner: Tool to run tasks under independent D-Bus sessions

The last 2 commits I still need to test on my system with all the Lomiri stuff, just threw them in here so those packages are less stale on arrival.

Working fine, keeping them in.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• 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
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 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
• Fits CONTRIBUTING.md.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/prs-ready-for-review/3032/2343

[SuperSandro2000]

not sure on the package set if it is done correct for cross

[OPNA2608]

I'm not sure if the package set is correctly written to support cross either, the approach was taken from the Deepin / DDE set. But most of the packages in it will use our qtbase where cross is borked anyway: #227900

[OPNA2608]

@SuperSandro2000 Is the uncertainty about the package set's cross-buildability a blocker for you (and thus blocked by qtbase itself having borked cross) or is there anything else you'd like me to change?

[OPNA2608]

@SuperSandro2000 I've tried locally adding something to the package set that doesn't need Qt & building it with --argstr crossSystem aarch64-linux and that works fine, so I think the package set is done correct for cross. Bump.

[SuperSandro2000]

@SuperSandro2000 Is the uncertainty about the package set's cross-buildability a blocker for you (and thus blocked by qtbase itself having borked cross) or is there anything else you'd like me to change?

Na, I was just curious and wanted to let you know that I do not know.

[SuperSandro2000]

If we missed something especially cross related we can fix that in another PR to not delay this one any longer.