build: start building with C++20 Standard

[rprospero]

This PR starts compiling with the C++20 standard. This causes some knock-on effects

• We no longer depend on the fmt formatting library
• We need at least GCC 13
• To retrieve GCC 13, we needed to upgrade to a more recent nixpkgs release, which brought on a patch upgrade of TBB
• We've also upgraded LLVM to version 17, which also upgrades clang-format from version 13 to version 17
• To get the appropriate clang for OS X, I've had to drop support for Intel Macs. To be honest, it should work on Macs running OS 14 or higher, but GitHub Actions don't provide Intel hardward for those OSes, so we wouldn't be able to test them.
• The QC checks now use the commands from the nix shell, to ensure that upgrades are kept in sync. This has resulted in some format changed with updated version.

The most interesting files to look at are:

• .github/workflows/qc/action.yml
• CMakeLists.txt
• src/gui/models/sortFilterProxy.h
• src/items/serialisers.cpp
• src/keywords/weightedModuleVector.cpp
• src/templates/vector3.h
• src/templates/vector4.h

A couple of notes to take while looking through the pr

• There is not standard equivalent of fmt::print, so I replaced
  those calls with std::cout
• std::format requires that the format string is known at
  compile time. This means that formats passed as a function or
  switched via a ternary expression cannot be used. The
  std::vformat function handles dynamic formats, though it
  requires an ugly wrapping of the parameters. For most of the
  ternary cases, I simply moved the conditional outside of the
  format call to regain the benefit of static format checking.
  Allegedly, C++26 will merge format and vformat.

I'll pull this out of draft once it compiles on all platforms and passes all tests.

[trisyoungs]

Like it. Worth doing for the formatting changes in the PCG headers alone!

[rprospero]

@trisyoungs I've moved in the copyright updates into this PR. I'm just looking to fix up the windows build. Or should we make that a separate PR, now that we at least have the QC working again.

[trisyoungs]

@rprospero I think, if it turns out to be a quick / easy fix then wrap it in to this PR so we can get the whole CI rolling again. If it turns out to be more of an effort, split it.