Part of #11704

• Updates OIDC and GitHub OAuth login to fetch set name from relevant claim fields
• Adds CODER_OIDC_NAME_FIELD as configurable source of user name claim
• Adds httpapi function to normalize a username such that it will pass validation
• Adds firstName / lastName fields to dev OIDC setup

Screenshots:

1. Post-OIDC login:
   

2. OIDC claims from DB:
   

NOTE: does not update "first-time setup" in the UI to allow setting username. This will be done in a separate PR.