feat: extension list UI (#4066)

extensions/package-manager/less/admin.less

@@ -2,6 +2,8 @@
 @import "admin/TaskOutputModal";
 @import "admin/QueueSection";
 @import "admin/ControlSection";
+@import "admin/DiscoverSection";
+@import "admin/ExtensionCard";
 
 .ExtensionManager-controlSection {
   > .container {
@@ -16,12 +18,6 @@
   gap: 4px;
 }
 
-.Form-group--danger {
-  border: 2px solid var(--alert-error-bg);
-  border-radius: var(--border-radius);
-  background-color: transparent;
-}
-
 .ButtonGroup--full {
   width: 100%;
   display: flex;
@@ -47,6 +43,7 @@
   column-count: 3;
   column-gap: 30px;
   flex-wrap: wrap;
+  margin-top: 24px;
 
   .FormSection {
     min-width: 300px;
@@ -63,11 +60,3 @@
     }
   }
 }
-
-.ExtensionManager-warnings {
-  margin-bottom: 24px;
-
-  > .Alert {
-    width: 100%;
-  }
-}