feat(dropdown): dropdown formatted with label

Supports the dropdown to be formatted with the label at left or
right position same as `labeled input` and `action input`.

This feature depends on the labeled input and only works when the
theme has enabled the labeled input variation.

src/definitions/modules/dropdown.less

@@ -1323,6 +1323,30 @@ select.ui.dropdown {
   }
 }
 
+& when (@variationInputLabeled) {
+  /*--------------------
+          Labeled
+  ---------------------*/
+
+  /* Regular Label on Left */
+  .ui.labeled.input:not([class*="corner labeled"]) .label:first-child + .dropdown {
+    border-top-left-radius: 0;
+    border-bottom-left-radius: 0;
+    border-left-color: transparent;
+  }
+
+  /* Regular Label on Right */
+  .ui[class*="right labeled"].input > .dropdown:not(:last-child) {
+    border-top-right-radius: 0 !important;
+    border-bottom-right-radius: 0 !important;
+    border-right-color: transparent !important;
+  }
+  .ui[class*="right labeled"].input > .dropdown + .label {
+    border-top-left-radius: 0;
+    border-bottom-left-radius: 0;
+  }
+}
+
 /*--------------
      Columnar
 ---------------*/