Fix output directory of files in client & when calling Blocks as function

[abidlabs]

Previously, different serializers saved output files in inconsistent places. This meant that if you used the client to do a prediction, it could save output files in various places -- including the working directory for the Gallery component (see #4494). This fixes that -- all of the serializers save output files to a folder created within the GRADIO_TEMP_DIR directory.

Test with:

import gradio as gr

demo = gr.Interface(
    lambda x:["cheetah.jpg"],
    inputs=[gr.Slider(value=3, minimum=1, maximum=3, step=1)],
    outputs=[gr.Gallery(columns=2, preview=True)],
)

demo(4)

demo = gr.Interface(
    lambda x:"cheetah.jpg",
    inputs=[gr.Slider(value=3, minimum=1, maximum=3, step=1)],
    outputs=[gr.Image()],
)

demo(4)

and so on.

Furthermore, if you are using the python Client, you can specify the output directory with a new output_dir parameter.

Closes: #4494
Closes: #4495

[gradio-pr-bot]

All the demos for this PR have been deployed at https://huggingface.co/spaces/gradio-pr-deploys/pr-4501-all-demos

[freddyaboulton]

@abidlabs is this ready? Got tagged for review but it's still a draft. Quick turnaround!

[abidlabs]

Just adding tests @freddyaboulton! Will open up soon

[freddyaboulton]

Looks good @abidlabs !

[abidlabs]

Thanks @freddyaboulton for the review! Will address the suggestions tomorrow

[abidlabs]

I'll need to release a new version of gradio_client for the regular tests to pass