fix: use canonical path in windows

[younger-1]

This fixes #953.

Relative upstream issue: neovim/neovim#16331

[younger-1]

When I simply use fs_realpath of libuv, the bug of #953 went away but it caused new error:

Error detected while processing BufEnter Autocommands for "*":
E5108: Error executing lua ...ata\site\pack\packer\opt\nvim-tree.lua/lua/nvim-tree.lua:164: bad argument #1 to 'fs_stat' (string expected, got nil)
stack traceback:
        [C]: in function 'fs_stat'
        ...ata\site\pack\packer\opt\nvim-tree.lua/lua/nvim-tree.lua:164: in function 'is_file_readable'
        ...ata\site\pack\packer\opt\nvim-tree.lua/lua/nvim-tree.lua:192: in function 'find_file'
        [string ":lua"]:1: in main chunk

It seems that the result of luv.fs_realpath(filepath) is nil which convinced me fs_realpath is async.
But it should be sync in this case, according to the doc of libuv...
https://github.com/kyazdani42/nvim-tree.lua/blob/9ad827789f8b01587dea5dd2d629206c847a26e2/lua/nvim-tree.lua#L191-L194

https://github.com/luvit/luv/blob/9d602ab12654d3adb53f34457390f534eb85f5d6/docs.md?plain=1#L2891-L2897

### `uv.fs_realpath(path, [callback])`

**Parameters:**
- `path`: `string`
- `callback`: `callable` (async version) or `nil` (sync version)
  - `err`: `nil` or `string`
  - `path`: `string` or `nil`

Could anyone knows this give some tips?

[kyazdani42]

could you rebase :) ?

[kyazdani42]

Also i'm not sure for your issue with realpath, might be related to windows somehow ?

[younger-1]

could you rebase :) ?

Done

[kyazdani42]

thanks :)