remove utils.images and required dependencies

[bch0w]

Description of the desired feature

Pyatoa's util.images.py utility script contains functions that are used to manipulate .png and .pdf files to combine waveform figures into single pdfs. These were required when Pyatoa contained most of the machinery to run within a larger SeisFlows workflow. However, Pyatoa has since moved to becoming a smaller dependency with less agency, and SeisFlows has consumed most of its larger workflow functions including image manipulation. It is therefore best to migrate all of the functions inside images.py to SeisFlows and remove the dependencies (Pillow, PyPDF2) from Pyatoa to make it a slimmer package. Currently no other classes/modules in Pyatoa import the images utilities so this should be a straightforward delete

Are you willing to help implement and maintain this feature?

Yes