Add final CCF overview plot to L2 QLP

[shalverson]

To help diagnose issues with the final CCF fits, both for stellar and calibration spectra, it would be helpful to have a zoomed in figure showing the full-chip CCF (all orders combined via their appropriate weights) with the fitted region highlighted.

Eventually, we'll want to also show the final CCF fit for each L2 file, like the example plot below, though this will require saving more parameters: