refactor: move init_default_autocmds to lua

The original motivation for this change came from developping
https://github.com/neovim/neovim/pull/22159, which will require adding
more autocommand creation to Neovim's startup sequence.

This change requires lightly editing a test that expected no autocommand
to have been created from lua.

runtime/lua/vim/_editor.lua

@@ -894,6 +894,26 @@ function vim._init_default_mappings()
   ]])
 end
 
+function vim._init_default_autocmds()
+  local nvim_terminal_augroup = vim.api.nvim_create_augroup('nvim_terminal', {})
+  vim.api.nvim_create_autocmd({ 'bufreadcmd' }, {
+    pattern = 'term://*',
+    group = nvim_terminal_augroup,
+    nested = true,
+    command = "if !exists('b:term_title')|call termopen(matchstr(expand(\"<amatch>\"), '\\c\\mterm://\\%(.\\{-}//\\%(\\d\\+:\\)\\?\\)\\?\\zs.*'), {'cwd': expand(get(matchlist(expand(\"<amatch>\"), '\\c\\mterm://\\(.\\{-}\\)//'), 1, ''))})",
+  })
+  vim.api.nvim_create_autocmd({ 'cmdwinenter' }, {
+    pattern = '[:>]',
+    group = vim.api.nvim_create_augroup('nvim_cmdwin', {}),
+    command = 'syntax sync minlines=1 maxlines=1',
+  })
+end
+
+function vim._init_defaults()
+  vim._init_default_mappings()
+  vim._init_default_autocmds()
+end
+
 require('vim._meta')
 
 return vim