[sim] Update thirdparty-imgui (#2552)

Updates the following dependencies:
- glfw to latest 3.3-stable
- imgui to 1.76
- stb to latest master

Removes libvulkan dependency.

Also adds implot.

shared/config.gradle

@@ -11,7 +11,7 @@ nativeUtils {
       niLibVersion = "2020.10.1"
       opencvVersion = "3.4.7-3"
       googleTestVersion = "1.9.0-4-437e100-1"
-      imguiVersion = "1.72b-4"
+      imguiVersion = "1.76-2"
     }
   }
 }