stream settings: Improve UI for editing stream permissions.

This now is much more similar to our normal settings UI.

static/styles/subscriptions.css

@@ -844,8 +844,7 @@
         }
     }
 
-    .stream-header,
-    .stream_setting_subsection_header {
+    .stream-header {
         white-space: nowrap;
 
         .stream-name {
@@ -911,6 +910,20 @@
         }
     }
 
+    .stream_setting_subsection_header {
+        display: flex;
+
+        .stream_permission_change_info {
+            margin: 12px auto 0 3px;
+        }
+
+        .button-group {
+            display: inline;
+            margin-left: auto;
+            align-self: center;
+        }
+    }
+
     .checkmark {
         display: none;
         margin-left: 5px;
@@ -1056,6 +1069,12 @@
     }
 }
 
+#stream_privacy_modal .modal-body {
+    .grey-box {
+        margin-bottom: 20px;
+    }
+}
+
 @media (width < $lg_min) {
     .subscriptions-container {
         max-width: 95%;
@@ -1192,6 +1211,14 @@
             }
         }
     }
+
+    #subscription_overlay .stream_setting_subsection_header {
+        display: block;
+
+        .stream_permission_change_info {
+            margin: 12px auto 0 3px;
+        }
+    }
 }
 
 #stream-creation #invites-warning-modal .modal-footer {