Display normalized values in spectrum viewer image view

[ashleymeigh2]

Issue Closes #2456

Description

• Updated spectrum viewer to display normalized values in the image view when normalization is enabled.
• Added get_normalized_averaged_image() to the model for normalized image data.
• Updated presenter to fetch and display the correct image based on normalization state.

Developer Testing

• Verified unit tests pass: python -m pytest -vs
• Tested normalized and non-normalized image rendering in the spectrum viewer.

Acceptance Criteria

• Unit tests pass: python -m pytest -vs
• Normalized values display when normalization is enabled.
• Non-normalized values display when normalization is disabled.
• Edge cases (e.g., missing stacks) handled correctly.

[samtygier-stfc]

I think the test is failing because self.view.normalisation_enabled() will be true by default in the mocked view. Might fix it to add self.view.normalisation_enabled.return_value = False in to the test.

[samtygier-stfc]

And it would be good to have a test for the new function in model_test.py