feat: option to combine completion.list.selection = "auto_insert" and "preselect"

[SamuelBorn]

Feature Description

Citation from default config:

-- 'preselect' will automatically select the first item in the completion list

-- 'auto_insert' will not select any item by default, and insert the completion items automatically when selecting them

I would like to the see another option that combines them both.
The documentation could be described as:

-- 'preselect_auto_insert' will automatically select the first item in the completion list, and insert the completion items automatically when selecting them

The default preselect action though should not trigger auto_insert as this would be annoying.

So to accept the first solution one still has to press the keyboard shortcut for accept or select_and_accept.

But after selecting with select_prev and select_next, auto_insert should trigger and accepting would no longer be necessary.

[ycycyyc]

After migrating from nvim-cmp, I kept the same behavior by using the following code.

  local list = require "blink.cmp.completion.list"
  local select = list.select
  list.select = function(idx, o)
    select(idx, o)
    local item = list.items[idx]
    require("blink.cmp.completion.trigger").suppress_events_for_callback(function()
      if idx and idx > 1 and item and list.config.selection == "preselect" then
        list.apply_preview(item)
      end
    end)
  end

it would be better if there is an option to combine "auto_inesrt " and "preselect".