add subpath support

[catalpaaa]

Describe what this pull request is trying to achieve.

add support to apply a custom subpath for launching gradio in, use when reverse proxied.

also maybe bump gradio to 3.28 after its out, i think it fixed some symlinks subpath thingy, it fixes #7028

Additional notes and description of your changes

issues for more context for what this fix

• [Bug]: Gradio login page is broken on gradio 3.23 #8897
• [Bug]: Cannot log in since the gradio "upgrade" from commit a9eab236 to commit 9e1afa9e #9003
• [Bug]: multiple serious UI issues after latest update #8894

Environment this was tested in

List the environment you have developed / tested this on. As per the contributing page, changes should be able to work on Windows out of the box.

• OS: ubuntu 22
• Browser: chrome, safari
• Graphics card: NVIDIA RTX 2080 8GB

Screenshots or videos of your changes

before:

after:

[AUTOMATIC1111]

don't put multiple unrelated things into same PR
webui.sh change should not be included also

[catalpaaa]

don't put multiple unrelated things into same PR

webui.sh change should not be included also

Sry, i don't know why but the GitHub desktop just keep including that

The bump for gradio is for a bug fix that fix symlink path on windows, and a bug fix for not releasing custom port during a restart