chore(ui): Custom providers drawer design update

[m-rgba]

Description

Design update for custom AI provider drawer.

Before	After

• ToDo: Need to update with docs link in the callout when we're ready to publish.
• Updated header area for height and font weight.
• Updated font to use Source Sans Pro / made typography feel right.
• Updated spacing between form elements.
• Made some tweaks to padding and sizing to prevent page overflow when the screen is short.
• Updated padding around the form.
• Adjusted button sizes on the clear buttons to match the inline inputs.
• Added a sample endpoint description to the base URL field.
• Made buttons full width - added submit / edit logic to the text.

Functional changes:

• Used the ResizeablDrawer cause we should probably center around using those for most of these non-peek drawers.
• Added default header and model rows to save on an action for adding a new row.
• Stripped empty headers (similar to the stripping model logic).
• Stripped the trailing / for the baseURL onSubmit (cause I do that all the time other places when I'm setting up custom models and it's annoying to debug).

[github-actions]

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[jwlee64]

im worried this might be confusing,
i used name because putting the token itself here doesnt work
you have to put the name and then add the name and token to the team secrets

[m-rgba]

Hey @jwlee64 - updated with a callout about the OpenAI compatible endpoint and more clarity around the API secret stuff. Have a look and let me know what you think.

[m-rgba]

Updated preview:
https://beta.wandb.ai/?betaVersion=9247c5b093dc72b1f083386763316195dc177fda