[feature] Add viz for model-obs 1D fit plot

## Description

It'd be great if there was a plot utility where one axis plots the model value, the second axis the obs value, so one can see how they collapse on 1:1 line.

## Implementation

Something similar is already implemented in `viz/interactiveWidgetProfile`. It is currently used in `tutorial2` to compare a float profile with the model, but potentially it can already be used for the whole dataset?

Start by reading the existing utility in viz/interactiveWidgetProfile and its use in tutorial2. Determine whether it can accept the whole dataset rather than a float profile, then verify that the resulting plot places model values and observation values on separate axes and makes their 1:1 relationship visible.

Written by the indexing model from the issue text.