Add convenience function for computing wavelength response

[nabobalis]

In GitLab by @wtbarnes on Sep 6, 2023, 11:16

Based on feedback from users, it would be convenient to have a single function that computes the wavelength response for a given channel and optionally a time. This would be a simple wrapper around the Channel object and wavelength_response method. It could also optionally take in a time in order to incorporate the channel degradation. This would reduce the number of steps need to compute the response. This function should also probably return the wavelength (or could optionally take in a wavelength and interpolate the response to it).