refactor: civil registeration staff member select for the correction requester

[jpye-finch]

Description

• Currently we have two options in the Correction requester page (Me & Another registration agent or field agent)
• This ticket is to combine the option into one 'Civil registeration staff member'
• On selection the user can search and select for the user
• Or if two tricky. Freeform enter their name

Acceptance criteria

GIVEN I am correcring a record
WHEN civil registeration staff member is requesting the change
THEN I can choose/enter the name of the user

Design

Dev tasks

• Task 1