Add backend validation for `Slider`, `Radio`, and `CheckboxGroup` (#2760)
* Add backend validation for form limitations [slider, radio, checkboxgroup]
Adds a preprocessing step for the slider, radio, and checkboxgroup components, as demonstrated in the issue "No backend validation for form limitations #1071."
* Update gradio/components.py
* Update gradio/components.py
* Update gradio/components.py
* fixes to logic
* updated tests
* formatting
* changelog fix
* revert test requirements
* delete artifact
* sanitizing docstrings
* comments
Co-authored-by: Abubakar Abid <abubakar@huggingface.co>