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/manage-users/edit-user-email.html

@@ -1,5 +1,4 @@
 {% extends "withnav_template.html" %}
-{% from "components/textbox.html" import textbox %}
 {% from "components/page-header.html" import page_header %}
 {% from "components/page-footer.html" import page_footer %}
 {% from "components/form.html" import form_wrapper %}
@@ -17,7 +16,7 @@
 
   <p class="govuk-body" id="user_name">This will change the email address for {{ user.name }}.</p>
   {% call form_wrapper() %}
-    {{ textbox(form.email_address, width='1-1', safe_error_message=True) }}
+    {{ form.email_address(param_extensions={"classes": "govuk-!-width-full"}, error_message_with_html=True) }}
     {{ page_footer('Save') }}
   {% endcall %}