[FIX] web: m2m tags overflow when too much tags

If too many tags (or too long tags) where present in a many2many tags
widgets, it could go over the field and cover other thing in the UI.

Now the field size expands with the content (and in a way it is more
visually similar before and after 'Edit' so it is nice).

closes #7579
opw-644236

addons/web/static/src/css/base.css

@@ -605,6 +605,7 @@
 }
 .openerp .oe_tags .text-wrap {
   width: 100% !important;
+  position: static;
 }
 .openerp .oe_tags .text-wrap textarea {
   width: 100% !important;

addons/web/static/src/css/base.sass

@@ -548,6 +548,7 @@ $sheet-padding: 16px
             min-width: 250px
         .text-wrap
             width: 100% !important
+            position: static
             textarea
                 width: 100% !important
         .text-core