Implements better error handling when a user enters an invalid 2FA recovery code. Upon entering an invalid code:
- Keep the user on the `/recover-2fa` page (This also makes it so the incorrect code remains in the form field so the user can see what they entered, if they mistyped the code, etc.)
- Show an inline error: "Invalid recovery code"
- Add recovery code enum and feature flag
- Update recovery code text and warning messages
- Log user in and redirect to two-factor settings page on valid recovery code
- Run full sync and handle login errors silently
- Move updated messaging behind feature flag
PM-15534
