bug: signature doesn't work when using the same buffer in different windows

[ofirgall]

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Neovim version (nvim -v)

v0.9.2-dev-a3889e7

Operating system/version

Ubuntu 22.04.1 LTS

Describe the bug

When I split a buffer to two windows the signature doesn't work on the right window but works on the left window.

I did some debugging, get_char function in lsp/signature gets the char by using the bufwinid.
bufwinid doesn't return the active window if the buffer exists in 2 windows therefore it doesn't work for the second window.

I changed vim.fn.bufwinid(buf) to vim.api.nvim_get_current_win() and it fixes the problem, but it doesn't take buf in account.

Steps To Reproduce

1. Open buffer
2. Make a split to the same buffer
3. Try to use the signature feature in the new window

Expected Behavior

Signature feature should work on the 2nd window as well

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",
  "folke/noice.nvim",
  -- add any other plugins here
}
require("lazy").setup(plugins, {
  root = root .. "/plugins",
})

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