Add confusion noise to the Mid sensitivity calculator

Derive the confusion noise for a range of beam sizes using a combination of real and model source count data at multiple frequencies (e.g. 150 MHz, 1.4 GHz and 5 GHz). Create a look-up table that can be used by the sensitivity calculator to obtain the confusion noise given the beam size and frequency.

The following should be provided to the Buttons team:

• The confusion noise look-up table
• Code to interpolate the confusion noise values in the look-up table
• Code to generate the look-up table
  The code will be written in a Jupyter notebook. The Buttons team could easily convert the code to a Python script for their use.

The sensitivity calculator should output the confusion noise, as well as the final Stokes I noise obtained by adding the confusion noise in quadrature with the thermal noise.