davinci-resolve: propagate desktop file & set mainProgram for studio version

[Naxdy]

Description of changes

• propagate .desktop file and icons for both regular and studio variants (studio variant has its icon renamed to avoid clashing with the regular variant)
• set mainProgram to be equal to davinci.pname which buildFHSEnv uses as the basis for the executable name

fixes #278133

Closes #278164

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• 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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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.

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[eclairevoyant]

Please drop the first commit, we don't use nixpkgs-fmt in nixpkgs.
Also, isn't there some overlap with #278164? (Though maybe that doesn't matter since there's not much activity on the other PR)

[Naxdy]

Please drop the first commit, we don't use nixpkgs-fmt in nixpkgs. Also, isn't there some overlap with #278164? (Though maybe that doesn't matter since there's not much activity on the other PR)

Yeah, it's basically the same thing, but the other PR seems abandoned :(

Will drop the fmt commit

[w-lfchen]

#278164 has been merged
if i'm not mistaken, this pr can be closed now but i'm not 100% sure

[Naxdy]

yep, looks good!