Fix loading latest history for file names with dots

[TheLounger]

Problem

When the most recent chat or instruct log is loaded, it fails when the file name has a dot in it. This seems to happen because .stem is being used twice:
https://github.com/oobabooga/text-generation-webui/blob/894e1a070067a7d9f22b032b53cdd3a3528dce53/modules/chat.py#L496 https://github.com/oobabooga/text-generation-webui/blob/894e1a070067a7d9f22b032b53cdd3a3528dce53/modules/chat.py#L513

The fix

Remove the extra .stem and use the "unique id" that comes from find_all_histories as is.
I've tested the fix in several ways, including crazy file names and directory junctions, but I'd love to hear if I missed some important reason for why the Path(...).stem was there.

Error logs

Starting up Webui, most recent history is named This.File.Name.Has.Several.Dots.json.

Traceback (most recent call last):
  File "E:\webui\installer_files\env\Lib\site-packages\gradio\queueing.py", line 407, in call_prediction
    output = await route_utils.call_process_api(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\gradio\route_utils.py", line 226, in call_process_api
    output = await app.get_blocks().process_api(
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\gradio\blocks.py", line 1550, in process_api
    result = await self.call_function(
             ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\gradio\blocks.py", line 1185, in call_function
    prediction = await anyio.to_thread.run_sync(
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\anyio\to_thread.py", line 33, in run_sync
    return await get_asynclib().run_sync_in_worker_thread(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\anyio\_backends\_asyncio.py", line 877, in run_sync_in_worker_thread
    return await future
           ^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\anyio\_backends\_asyncio.py", line 807, in run
    result = context.run(func, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\installer_files\env\Lib\site-packages\gradio\utils.py", line 661, in wrapper
    response = f(*args, **kwargs)
               ^^^^^^^^^^^^^^^^^^
  File "E:\webui\modules\chat.py", line 514, in load_latest_history
    history = load_history(unique_id, state['character_menu'], state['mode'])
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "E:\webui\modules\chat.py", line 524, in load_history
    f = json.loads(open(p, 'rb').read())
                   ^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'logs\\chat\\Ann\\This.File.Name.Has.Several.json'

Checklist

• I have read the Contributing guidelines.

[oobabooga]

That's correct, I didn't notice that .stem was being used twice. Thanks for the fix!