feat(menu): simplify calculations for selection

[vdbe]

When using a negative count for Menu:select_next don't go into negative indices instead rollover to the last entry.

This simplifies for example the following logic:

local next = function(direction, key)
  return function()
    if care.api.is_open() then
      -- Post PR
      care.api.select_next(direction)

      -- Pre PR
      -- if direction >= 0 then
      --   care.api.select_next(direction)
      -- else
      --   care.api.select_prev(-direction)
      -- end
    elseif vim.snippet.active { direction = direction } then
      vim.snippet.jump(direction)
    elseif key ~= nil then
      vim.api.nvim_feedkeys(vim.keycode(key), "n", false)
    else
      care.api.complete()
    end
  end
end

vim.keymap.set("i", "<c-n>", next(1))
vim.keymap.set("i", "<c-p>", next(-1))

[max397574]

would be nice if you could squash and adapt the commit message and pr title to the actual changed (e.g. feat(menu): simplify calculations for selection)
so we get a nice commit history

[max397574]

thank you for your contribution