Z-2276/Z-2275: Project & Branch switchers (#2662)

This PR adds project and branch switchers in top left corner. 

Release Notes:
- Added a project & branch switcher under project name.

styles/src/style_tree/picker.ts

@@ -110,5 +110,23 @@ export default function picker(): any {
                 top: 8,
             },
         },
+        header: {
+            text: text(theme.lowest, "sans", "variant", { size: "xs" }),
+
+            margin: {
+                top: 1,
+                left: 8,
+                right: 8,
+            },
+        },
+        footer: {
+            text: text(theme.lowest, "sans", "variant", { size: "xs" }),
+            margin: {
+                top: 1,
+                left: 8,
+                right: 8,
+            },
+
+        }
     }
 }