[feature] Add ability for attendee to add a "preferred name" that is different from their legal name.

[ksonney]

As an Attendee, I should be able to set my "preferred name" if it differs from my legal name.
As a staffer, I should be able to see the user's preferred name as the primary name, and before the legal name.

Reasoning : In Security, we regularly look up people as we do prop checks. It is VERY easy for us to dead-name a trans person, and I would like to have some safeguards in place to prevent this with Super 2023.

[kitsuta]

Summarizing outside conversation: the first name/last name is already the 'preferred' name, but it'd help to make the legal name less prominent/accessible to staff who don't need it.