[FIX] web: horizontal scrollbar in form without sheet

before this commit: when form view have buttonbox or notebook tag and form does
not have sheet tag then form will have horizontal scrollbar in screen, this is
because we added scss mixin which always add negative margin of 32px because we
added mixin by considering form will have sheet tag and because of that when
form does not have sheet tag it shows useless horizontal scrollbar.

after this commit: if formview does not have sheet tag and form contains button
box or notebook tag then form will be displayed properly without unnecessary
horizontal scrollbar.

task-2411627

closes odoo/odoo#63961

Related: odoo/enterprise#15519
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>

addons/web/static/src/scss/form_view.scss

@@ -5,6 +5,9 @@
         padding-left: $o-horizontal-padding*2;
     }
 }
+@mixin o-form-nosheet-inner-left-padding {
+    padding-left: $o-horizontal-padding;
+}
 @mixin o-form-sheet-inner-right-padding {
     padding-right: $o-horizontal-padding;
     @include media-breakpoint-between(lg, xl, $o-extra-grid-breakpoints) {
@@ -21,6 +24,11 @@
     }
 }
 
+@mixin o-form-nosheet-negative-margin {
+    margin-left: -$o-horizontal-padding;
+    margin-right: -$o-horizontal-padding;
+}
+
 .o_form_view {
     background-color: $o-view-background-color;
 
@@ -159,6 +167,9 @@
         .o_form_statusbar {
             margin: (-$o-sheet-vpadding) (-$o-horizontal-padding) $o-sheet-vpadding (-$o-horizontal-padding);
         }
+        .oe_button_box {
+            @include o-form-nosheet-negative-margin;
+        }
     }
 
     // Non-chatter rules