nvim: Switch to clangd and use libcxx to support c++23 headers

For some fucking unknown reason the clang-tools package doesn't build
with libcxx by default and thus doesn't have the print header from C++23
which I need. I also don't know if they're fucking using the gcc13 c++
stdlib because the gcc14 one FUCKING HAS THE HEADER. I lost hours of
life which I am never going to get back to this fucking bullshit.

dotfiles/nvim/lua/plugins/lsp/c.lua

@@ -1,5 +1,5 @@
 return function ()
-  require"lspconfig".ccls.setup {
+  require"lspconfig".clangd.setup {
     capabilities = require"cmp_nvim_lsp".default_capabilities()
   }
 end

modules/packages/nvim.nix

@@ -18,10 +18,12 @@
         lua-language-server
         nodePackages.intelephense
         nodePackages.typescript-language-server
-        ccls
+        (llvmPackages_19.clang-tools.override {
+          enableLibcxx = true;
+        })
         ripgrep
         nil
-        gcc
+        gcc14
         basedpyright
         rust-analyzer
         zathura