add script to update vscode extensions

[schuelermine]

• vscode/extensions/update_installed_exts.sh: log on download failure instead of early exit
• vscode/extensions/update_installed_exts.sh: add json output format
• vscode/extensions: add script to write new versions from update_installed_exts.sh

Obsoletes #388747.

Could use some polish, or comments. But it works.

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/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 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.

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[drupol]

I think you should join the force and contribute in this PR: #389585

[drupol]

@schuelermine Do you mind testing the script from #389585 ?

[drupol]

@schuelermine Can we close this PR ?

[schuelermine]

@drupol Yes, I will cherry-pick one of these commits into a new PR