pythonPackages: default to qt514

[Galagora]

Motivation for this change

Essentially a partial revert of the changes made #97586, which fixes Python QT packages that aren't wrapped well and leaves the version configurability for those that are. This should sort out the likes of #98067 and #98069.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• 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 nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[gebner]

FreeCAD is also broken for this reason. It currently uses libsForQt514, but this breaks when using pyside2 built with Qt 5.15. Upgrading to Qt 5.15 isn't straightforward either, because qtwebkit doesn't build.

[gebner]

cc @petabyteboy @ttuegel @raboof

[Galagora]

Fixed (a4e50bb).

[FRidh]

a4e50bb reverted the use of 5.15 everywhere. qt version can now be set per application by overriding pkgs c88f3ad. See qutebrowser as example 2daf570.

[gebner]

@FRidh The override doesn't seem to work for me at all (this is on current master):

$ nix repl .
nix-repl> python38Packages.pyqt5.buildInputs
[ «derivation /nix/store/sgkk9zpr8ans81f0g5wpi5y6yy0inq1s-dbus-1.12.20.drv»
  «derivation /nix/store/2i6wvm2jqw83qq7rcsh7acdkyisdc3bw-qtbase-5.15.0.drv»
  «derivation /nix/store/q0fg5km866036a1y86rw4bp572v7pwyx-qtsvg-5.15.0.drv»
  «derivation /nix/store/wa02900pzn8q4ylkpkzyh1bsbzgfbv6r-qtdeclarative-5.15.0.drv» ]

nix-repl> python38Packages.shiboken2.buildInputs
[ «derivation /nix/store/qfkak7qkx2cgwqrs9qy275dxfd501c5z-clang-7.1.0.drv»
  «derivation /nix/store/xy9dx0qx4gcnph7bz0g6d616ls5vm0j6-python3-3.8.5.drv»
  «derivation /nix/store/2i6wvm2jqw83qq7rcsh7acdkyisdc3bw-qtbase-5.15.0.drv»
  «derivation /nix/store/2kdzq789vahilya85jbwd1dipazvnx9g-qtxmlpatterns-5.15.0.drv» ]

[FRidh]

Yes, I did not test it correctly. See the discussion in #98197.