Add max width to user and project settings

What does this MR do and why?

Adds max width to inputs in:

• User settings
• Project settings

Follow-up to Set max width on user preference inputs (!127909 - merged)

What does this MR not do?

• Max width for the entire page (out of scope)
• Group settings
• The rest of the project settings (separate MR)
• The email label bug (fixed in Namepace email address label (!129291 - merged))

Screenshots or screen recordings

User settings

Before	After

Project settings

Before	After

How to set up and validate locally

• User settings
• Project settings (first half up until Repository settings)

UX Paper Cuts 16.3 → Settings UI, part 2 (#417912 - closed)