Redo Learn/Concepts section and figure out what diagrams we need

[catmcgee]

[catmcgee]

put in design request for diagrams
animations even cooler!

[critesjosh]

There are a bunch of diagrams that have not been added to the appropriate docs pages yet, here: https://drive.google.com/drive/folders/1SAEcPWtafhoNvKiJkcIfnboagqZMO90a, also mentioned here #308

[catmcgee]

make overview page more about intuitions, why, how
https://docs.aztec.network/aztec/overview