Warn users when adding SSH keys of weaker types or smaller lengths

Follow up from https://gitlab.com/gitlab-org/gitlab/-/issues/432492+. Add a message in GitLab UI SSH key upload section to inform users that they are trying to use an older/less secure SSH key type or a key of < 2048 bit length. While the key type/length can be enforce by administrators https://docs.gitlab.com/ee/security/ssh_keys_restrictions.html we don't inform individual users if they are using a less secure key type outside of that setting.

Also see https://gitlab.com/gitlab-org/gitlab/-/issues/432492#note_1662509738+ for what messaging exists today