Prevent 500 errors on FIPS systems when user password is too short

What does this MR do and why?

On Ubuntu 22.04 FIPS system, attempting to hash a password less than 8 characters results in:

OpenSSL::KDF::KDFError (PKCS5_PBKDF2_HMAC: invalid key length)

Previously the password length was only checked in a Devise validator, but this is too late for OpenSSL. Fix this by doing this check in Users::UpdateService.

Relates to https://gitlab.com/gitlab-com/request-for-help/-/issues/3526

References

Screenshots or screen recordings

How to set up and validate locally

1. Install Ubuntu 22.04 Pro FIPS system.
2. Install GitLab.
3. Attempt to change a password.

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