PB-108 add a way to keep content from before this story compatible to this implementation

Author: paras89

app/code/Magento/PageBuilder/view/adminhtml/pagebuilder/content_type/column.xml

@@ -23,10 +23,12 @@
         </breakpoints>
         <parents default_policy="deny">
             <parent name="column-line" policy="allow"/>
+            <parent name="column" policy="allow"/>
         </parents>
         <children default_policy="allow">
             <child name="row" policy="deny"/>
             <child name="column" policy="deny"/>
+            <child name="column-line" policy="deny"/>
         </children>
         <is_system>false</is_system>
         <appearances>

app/code/Magento/PageBuilder/view/adminhtml/pagebuilder/content_type/column_group.xml

@@ -24,6 +24,7 @@
         </parents>
         <children default_policy="deny">
             <child name="column-line" policy="allow"/>
+            <child name="column" policy="allow"/>
         </children>
         <appearances>
             <appearance default="true"

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/content-type/column-group/_default.less

@@ -24,6 +24,12 @@
         box-sizing: border-box;
         width: 100%;
 
+        &.no-column-line {
+            .element-children {
+                display:flex;
+            }
+        }
+
         .drop-placeholder {
             background: rgba(142, 0, 6, .3);
             bottom: 0;

app/code/Magento/PageBuilder/view/adminhtml/web/css/source/content-type/column/_default.less

@@ -27,7 +27,7 @@
 }
 
 .pagebuilder-content-type.pagebuilder-column {
-    min-height: inherit;
+    min-height: 150px;
 
     &.empty-container {
         min-height: 300px;