add section icon and use in dashboard edit mode (#38575)

frontend/src/metabase/dashboard/components/DashboardHeader/DashboardHeader.tsx

@@ -428,7 +428,7 @@ class DashboardHeaderContainer extends Component<DashboardHeaderProps> {
             <span>
               <DashboardButtonTooltip label={t`Add section`}>
                 <DashboardHeaderButton aria-label={t`Add section`}>
-                  <Icon name="table_spaced" size={18} />
+                  <Icon name="section" size={18} />
                 </DashboardHeaderButton>
               </DashboardButtonTooltip>
             </span>

frontend/src/metabase/ui/components/icons/Icon/icons/index.ts

@@ -257,6 +257,8 @@ import recents_component from "./recents.svg?component";
 import recents_source from "./recents.svg?source";
 import revert_component from "./revert.svg?component";
 import revert_source from "./revert.svg?source";
+import section_component from "./section.svg?component";
+import section_source from "./section.svg?source";
 import share_component from "./share.svg?component";
 import share_source from "./share.svg?source";
 import sql_component from "./sql.svg?component";
@@ -943,6 +945,10 @@ export const Icons = {
     component: search_component,
     source: search_source,
   },
+  section: {
+    component: section_component,
+    source: section_source,
+  },
   segment: {
     component: segment_component,
     source: segment_source,

frontend/src/metabase/ui/components/icons/Icon/icons/section.svg

+<svg width="16" height="16" fill="currentColor" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M1.75 5c0-.966.784-1.75 1.75-1.75h9c.966 0 1.75.784 1.75 1.75v6a1.75 1.75 0 0 1-1.75 1.75h-9A1.75 1.75 0 0 1 1.75 11V5Zm1.75-.25a.25.25 0 0 0-.25.25v6c0 .138.112.25.25.25H6v-6.5H3.5Zm9 6.5h-5v-2.5h5.25V11a.25.25 0 0 1-.25.25Zm.25-4V5a.25.25 0 0 0-.25-.25h-5v2.5h5.25Z"/></svg>