Convert web tests to browser tests for user module part-2

Follow-up to #2870465: Convert web tests to browser tests for user module →

Conversion scope

- UserAdminSettingsFormTest extending SystemConfigFormTestBase which is getting converted here #2867154: Form: Convert system functional tests to phpunit →
- UserPasswordResetTest should be split into JTB and BTB #2809543: Convert AJAX part of \Drupal\user\Tests\UserPasswordResetTest to WebDriverTestBase →
- UserBlocksTest requires setRawContent to be available in BTB
- UserRegistrationTest should be split into JTB and BTB
- UserAdminLanguageTest requires constructFieldXpath which is getting converted here #2868019: AssertLegacyTrait field assertions not compatible with Simpletest assertions →
- UserCreateTest See more background details here #2870465-17: Convert web tests to browser tests for user module →
- UserAdminSettingsFormTest to KTB