Set appropriate labels in the user entity base field definition

Problem/Motivation

Currently UserStorageController::baseFieldDefinitions() (/core/modules/user/lib/Drupal/user/UserStorageController.php) uses the label "Name" for different base field definitions. That's not really a good idea :D
Snipped:

...
    $properties['name'] = array(
      'label' => t('Name'),
      'description' => t('The name of this user'),
      'type' => 'string_field',
      'settings' => array('default_value' => ''),
    );
    $properties['pass'] = array(
      'label' => t('Name'),
      'description' => t('The password of this user (hashed)'),
      'type' => 'string_field',
    );
    $properties['mail'] = array(
      'label' => t('Name'),
      'description' => t('The e-mail of this user'),
      'type' => 'string_field',
      'settings' => array('default_value' => ''),
    );
...

Proposed resolution

Set speaking labels for all field definitions.

Remaining tasks

Create a patch. Thanks!

User interface changes

none

API changes

none

Related Issues

Problem found in #1777956-82: Provide a way to define default values for entity fields