Add `ModelChain` temperature comparison example to `system-models`

[aman-coder03]

Is your feature request related to a problem? Please describe.
The system-models example gallery currently has only 1 example. It is a detailed real-world case but there isn’t a example that demonstrates how to customize ModelChain for common use cases

Describe the solution you'd like
I would like to add a small Sphinx-gallery example comparing different temperature_model options in ModelChain (maybe sapm vs faiman or we can have a discussion over that) showing how that affects cell temperature and AC output

Describe alternatives you've considered
I have not considered other alternatives at this point

Additional context
I will follow the same Sphinx-gallery structure as the existing examples and keep this one small and self-contained. The idea is to complement the current OEDI example

Happy to adjust based on discussions and feedbacks.