Add compatibility with "suda" plugin (lambdalisue/vim-suda)

[x3rAx]

When using suda to open root files, windsurf fails to complete and spams error notifications:

completion request failed: {"code":"unknown","message":"invalid_argument: empty share name for UNC-like path: //suda:///path/to/file.ext"}

While debugging I found that in the completion request, absolute_uri is broken and workspace_uri sometimes is a relative path:

{
  absolute_uri = "file://suda:///path/to/file.ext",
  cursor_offset = 4,
  cursor_position = {
    col = 4,
    row = 0
  },
  editor_language = "plaintext",
  language = 30,
  line_ending = "\n",
  text = "asdf\n",
  workspace_uri = "file://."
}

This PR adds relative path resolving and the removal of suda:// from the beginning of file paths to the util.get_uri() method.

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