Extend user_login_state with SAML connector info and grants

[kopiczko]

Needed for https://github.com/gravitational/teleport.e/pull/7168

[kopiczko]

For reference the old UpdatePreservedAttributes:

func UpdatePreservedAttributes(ctx context.Context, user services.UserState, ulsService services.UserLoginStates) error {
	// Use the new/existing GitHubIdentities.
	// TODO(greedy52) implement a way to remove the identity or find a way to
	// avoid keeping the identity forever in user login state.
	if len(user.GetGithubIdentities()) > 0 {
		return nil
	}

	// Find the old state if exists.
	old, err := ulsService.GetUserLoginState(ctx, user.GetName())
	if err != nil {
		if trace.IsNotFound(err) {
			return nil
		}
		return trace.Wrap(err)
	}

	if githubIdentities := old.GetGithubIdentities(); len(githubIdentities) > 0 {
		user.SetGithubIdentities(githubIdentities)
	}
	return nil
}

[kopiczko]

Friendly ping @smallinsky