Replace manual input from `ImGui::InputText` with better alternative for 3D model selection

[mrparmesan01]

Brief Task Overview

Rather then having an input text for manually typing in the path to the 3D model. This should be changed to being a button (ImGui::Button).

These are some ideas, I have in mind:

• Button using ImGui::Button to select what 3D model path to load.
• Creating a dropdown button box to select the available 3D models + relative path specifically set in the content browser panel.

What does task completion look like?

This task when completed should give us the ability to select the 3D models rather then inputting the path to the 3D model specifically.