Convert EmailFields to GovukEmailFields

Changes those fields (and sometimes also regular text input fields)
 in the following forms:
- LoginForm
- RegisterUserForm
- ChangeEmailForm
- FeedbackOrProblem
- AcceptAgreementForm
- ChangeNameForm (only name field here, but used in the same template
field as ChangeEmailForm here: app/templates/views/user-profile/change.html)

Also includes changes to templates that use this form
and associated tests.

app/templates/views/forgot-password.html

@@ -1,5 +1,4 @@
 {% extends "withoutnav_template.html" %}
-{% from "components/textbox.html" import textbox %}
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/form.html" import form_wrapper %}
 
@@ -16,7 +15,7 @@ Create a new password
     <p class="govuk-body">We’ll send you an email to create a new password.</p>
 
     {% call form_wrapper() %}
-      {{ textbox(form.email_address, safe_error_message=True) }}
+      {{ form.email_address(error_message_with_html=True) }}
       {{ page_footer("Send email") }}
     {% endcall %}