bug: window centering isn't correct when border isn't equal 'none'

[dtcyganok]

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• I have read all the lazy.nvim docs
• I have searched the existing issues of lazy.nvim
• I have searched the existing issues of plugins related to this issue

Neovim version (nvim -v)

v0.9.0

Operating system/version

Linux

Describe the bug

The window centering isn't correct when border isn't equal 'none'. Perhaps the window position calculation doesn't include logic about borders.

Steps To Reproduce

Set the ui option border = 'rounded'

Expected Behavior

The window centered correctly.

Repro

-- DO NOT change the paths and don't remove the colorscheme
local root = vim.fn.fnamemodify("./.repro", ":p")

-- set stdpaths to use .repro
for _, name in ipairs({ "config", "data", "state", "cache" }) do
  vim.env[("XDG_%s_HOME"):format(name:upper())] = root .. "/" .. name
end

-- bootstrap lazy
local lazypath = root .. "/plugins/lazy.nvim"
if not vim.loop.fs_stat(lazypath) then
  vim.fn.system({ "git", "clone", "--filter=blob:none", "https://github.com/folke/lazy.nvim.git", lazypath, })
end
vim.opt.runtimepath:prepend(lazypath)

-- install plugins
local plugins = {
  "folke/tokyonight.nvim",
  -- add any other plugins here
}
require("lazy").setup(plugins, {
  root = root .. "/plugins",
  ui = {
    border = 'rounded',
  },
})

vim.cmd.colorscheme("tokyonight")
-- add anything else here