home: vim: null-ls: fix deprecated builtins

`none-ls` deprecated a lot of unmaintained builtins, or ones that they
find has been replaced by a compete LSP server.

This removes those deprecated builtins, or uses a shim until I migrate
to the relevant LSP configuration (for `bash-language-server`).

modules/home/vim/default.nix

@@ -68,6 +68,7 @@ in
       lsp-format-nvim # Simplified formatting configuration
       lsp_lines-nvim # Show diagnostics *over* regions
       none-ls-nvim # LSP integration for linters and formatters
+      none-ls-shellcheck-nvim # shellcheck shim for none-ls
       nvim-treesitter.withAllGrammars # Better highlighting
       nvim-treesitter-textobjects # More textobjects
       nvim-ts-context-commentstring # Comment string in nested language blocks

modules/home/vim/plugin/settings/null-ls.lua

@@ -28,14 +28,6 @@ null_ls.register({
     }),
 })
 
--- Haskell
-null_ls.register({
-    null_ls.builtins.formatting.brittany.with({
-        -- Only used if available
-        condition = utils.is_executable_condition("brittany"),
-    }),
-})
-
 -- Nix
 null_ls.register({
     null_ls.builtins.formatting.nixpkgs_fmt.with({
@@ -50,16 +42,6 @@ null_ls.register({
 
 -- Python
 null_ls.register({
-    null_ls.builtins.diagnostics.flake8.with({
-        -- Only used if available, but prefer pflake8 if available
-        condition = function()
-            return utils.is_executable("flake8") and not utils.is_executable("pflake8")
-        end,
-    }),
-    null_ls.builtins.diagnostics.pyproject_flake8.with({
-        -- Only used if available
-        condition = utils.is_executable_condition("pflake8"),
-    }),
     null_ls.builtins.diagnostics.mypy.with({
         -- Only used if available
         condition = utils.is_executable_condition("mypy"),
@@ -81,13 +63,13 @@ null_ls.register({
 
 -- Shell (non-POSIX)
 null_ls.register({
-    null_ls.builtins.code_actions.shellcheck.with({
+    require("none-ls-shellcheck.diagnostics").with({
         -- Restrict to bash and zsh
         filetypes = { "bash", "zsh" },
         -- Only used if available
         condition = utils.is_executable_condition("shellcheck"),
     }),
-    null_ls.builtins.diagnostics.shellcheck.with({
+    require("none-ls-shellcheck.code_actions").with({
         -- Show error code in message
         diagnostics_format = "[#{c}] #{m}",
         -- Require explicit empty string test, use bash dialect
@@ -110,13 +92,13 @@ null_ls.register({
 
 -- Shell (POSIX)
 null_ls.register({
-    null_ls.builtins.code_actions.shellcheck.with({
+    require("none-ls-shellcheck.diagnostics").with({
         -- Restrict to POSIX sh
         filetypes = { "sh" },
         -- Only used if available
         condition = utils.is_executable_condition("shellcheck"),
     }),
-    null_ls.builtins.diagnostics.shellcheck.with({
+    require("none-ls-shellcheck.code_actions").with({
         -- Show error code in message
         diagnostics_format = "[#{c}] #{m}",
         -- Require explicit empty string test