[FIX] base: inline buttons was breaking into multiple lines (outlook hack)

Because we converted buttons into tables so inline buttons was
breaking into multiple lines so we need to add display inline and vertical align
properties in tables.

We allowed display property from mail sensitizer whitelist.

Because in this commit https://github.com/odoo/odoo/commit/cf15030ed09f7479f5b2701ba101a5bed71f7409
we use display property for align items

addons/web_editor/static/src/js/editor/transcoder.js

@@ -287,7 +287,7 @@ function classToStyle($editable) {
 
         // Outlook
         if (node.nodeName === 'A' && $target.hasClass('btn') && !$target.hasClass('btn-link') && !$target.children().length) {
-            var $hack = $('<table class="o_outlook_hack" style="display: inline-table;"><tr><td></td></tr></table>');
+            var $hack = $('<table class="o_outlook_hack" style="display: inline-table;vertical-align:middle"><tr><td></td></tr></table>');
             $hack.find('td')
                 .attr('height', $target.outerHeight())
                 .css({

odoo/tools/mail.py

@@ -45,7 +45,7 @@ class _Cleaner(clean.Cleaner):
     _style_whitelist = [
         'font-size', 'font-family', 'font-weight', 'background-color', 'color', 'text-align',
         'line-height', 'letter-spacing', 'text-transform', 'text-decoration',
-        'float', 'vertical-align',
+        'float', 'vertical-align', 'display',
         'padding', 'padding-top', 'padding-left', 'padding-bottom', 'padding-right',
         'margin', 'margin-top', 'margin-left', 'margin-bottom', 'margin-right',
         # box model