curl_multibyte: support Windows paths longer than MAX_PATH

curl_multibyte: support Windows paths longer than MAX_PATH

- Add a helper function for the Windows file wrapper functions that will
  normalize a long path (or a filename in a long path) and add the
  prefix `\\?\` so that Windows will access the file.

Prior to this change if a filename (when normalized internally by
Windows to its full path) or a path was longer than MAX_PATH (260) then
Windows would not open the path, unless it was already normalized by the
user and had the `\\?\` prefix prepended.

The `\\?\` prefix could not be passed to file:// so for example
something like file://c:/foo/bar/filename255chars could not be opened
prior to this change.

There's some code in tool_doswin that will need to be modified as well
to further remove MAX_PATH (aka PATH_MAX) limitation.

Ref: https://github.com/curl/curl/issues/8361
Ref: https://github.com/curl/curl/pull/13512
Ref: https://learn.microsoft.com/en-us/dotnet/standard/io/file-path-formats
Ref: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation

Closes https://github.com/curl/curl/pull/13522