Logical size + WAL pricing

This is a simulator to calculate the tenant size in different scenarios, using the "Logical size + WAL" method. Makefile produces diagrams used in a private presentation:

https://docs.google.com/presentation/d/1OapE4k11xmcwMh7I7YvNWGC63yCRLh6udO9bXZ-fZmo/edit?usp=sharing