A form view record may be saved even if the record is displayed in
readonly (e.g. when a button in the form view is clicked). When
this happened, if there were an html field with html_frame widget
in the form, it crashed (e.g. in Email Marketing > Mass Mailings >
open one > click on Test Mailing).

The translate feature of widgets html and html_frame had been
broken by the new views refactoring. This commit restores it for
the html widget, and removes it completely for html_frame as it
wasn't working correctly before the new views anyway (moreover,
it had already been disabled for mass_mailing: de403dc1ab440b9b08ea7fce189cd157745dfe74).

This commit also ensures that the changes are correctly saved for
the html_frame widget. Note that this widget still needs to be
converted to our new coding guidelines.

Creating and editing mass mailing in multiple language is managed with
the change 05daa15.

But currently the language the mass mailing is sent in, is the language
of the "Process Mass Mailing Queue" (root user if not changed) so all
the recipients will receive the mail in the root user language has at
the time the given batch of mails is sended.

So this is different from what someone could expect by it being
translatable. In any case the recipients list could be based on a lead,
a partner a mass mailing contact or other and a language could not be
determinable in stable (a mass mailing contact does not have a language
for example).

If the system worked, there is also a usability downside in the meaning
that someone could duplicate a mail and not check all translation and
not be aware that the mail he see is maybe not the mail that will be
received (if translations have not all been completed).

In stable to have the same behavior in any case and lessen the usability
burden of users thinking erroneously the mass mailing may be sent in
several languages depending on a not-existing heuristic, this changeset
remove the translatability of mass mailing content.

This has the following effect:

no translation editing appear,
the mass mailing is edited and sent in one and the same language,
If someone want to send a mass mailing in several language, currently in
Odoo it would then require to:

duplicate the mass mailing,
change the domains of recipients base on choosen heuristic,
edit the duplicated mass mailing in the choosen language

opw-746445
opw-746776
closes #17718

set_value doesn't exist anymore. Instead use _setValue.

Also adds body_html to the blacklisted fields. Because that tends to
be quite long as well.

If the method commitChange from the widget FieldTextHtmlSimple was
called in mode=readonly, a traceback was displayed.  This is not very
common, because most save operations are done in mode=edit, but it can
happen in readonly mode: when the user clicks on an action button, then
the form view is saved, if necessary.

To reproduce this bug, just open a form view for res.users, and click on
the Change Password button.