vimPlugins: add ddc.vim and related plugins

[euank]

Description of changes

This adds the most commonly used set of ddc.vim plugins, or at least the set I use as part of my completion setup.

You can read more about ddc.vim over here: https://github.com/Shougo/ddc.vim

I've manually tested that these plugins work with my vim setup, and so far I've been maintaining an overlay for them. I'm hoping to be able to upstream them so others can benefit, and to simplify my own setup.

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.

[PerchunPak]

Those plugins depend on each other, could you please specify it similar to here?

[euank]

I verified the rebased-and-updated plugins in this PR still work with my vim setup!

Other than needing to still add the pum dependency (per comment thread above), I'm happy with this.

For anyone curious, my setup/use of these is over here, with these two PRs pulled in via an overlay.

[euank]

Now that the pum-vim PR merged, I've updated ddc-ui-pum to have that dependency; as far as I know, this is good to go!

[PerchunPak]

LGTM! Thanks!

CC @teto

[teto]

shouldn't that depend on a deno runtime somewhow ?

[euank]

They do indirectly!

denops-vim depends on deno here, ddc-vim depends on denops-vim, and all of these depend on ddc-vim.

I could explicitly add the denops dependency for all of them as well, but I believe as-is they'll always pull in deno via denops.

[teto]

my bad, was too lazy to check it out. Patching denops-vim (vimPlugins in general is tough). Is there a way to setup the path towards deno without patching the plugin, via configuration for instance, like vim.g.denops_runtime = ....
It's tangential to this PR that I approve, just curious.

[euank]

There's indeed the g:denops#deno setting, so people can override it if they want that way.

The current approach feels nice to me, since changing that external config's default value via adding an extra autoload file or such would, well, change the observable default value.

[teto]

thanks. Good to know. There is no clear stance on how to package the vim plugins. I would like to avoid patching as much as possible because it's bad practice (makes upstream debugging harder) but alternatives are not great for now.
I am thinking about having the neovim wrapper collect configurations from the plugins and autoadd it to its config ?!
You can read about this here #172538.
Waiting for CI before merge