[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.

simulation/halsim_gui/build.gradle

@@ -33,7 +33,7 @@ if (!project.hasProperty('onlylinuxathena') && !project.hasProperty('onlylinuxra
                 } else if (it.targetPlatform.operatingSystem.isMacOsX()) {
                     it.linker.args << '-framework' << 'Cocoa' << '-framework' << 'IOKit' << '-framework' << 'CoreFoundation' << '-framework' << 'CoreVideo'
                 } else {
-                    it.linker.args << '-lX11' << '-lvulkan'
+                    it.linker.args << '-lX11'
                 }
             }
         }