Skip password policy validation when admin creates user with notify flag

Problem/Motivation

As administrator, I can create user entities without setting the password, but instead a notification e-mail is sent.
In this scenario, the password fields are hidden, however, the password length validation is triggered and the following error message is shown: Password length must be at least @count characters.

Steps to reproduce

1. Enable password_policy and password_policy_length modules
2. Login as administrator
3. Go to "/admin/people/create"
4. Enable the "Notify user of new account" option
5. Enter username and e-mail address and hit "Create account"

Proposed resolution

The resolution is to skip the password validation if the "Notify user of new account" option is set to true.

User interface changes

No interface changes

API changes

No API changes

Data model changes

No data model changes