Previously we had to specify the forward and backwards feature dependencies separately which was error prone. And as dependencies have gotten more complex it was hard to be sure the transitive dependencies were handled correctly. The way it was written was also not super readable.
This patch replaces everything with a table that lists what features a feature is dependent on directly. Then we just have to recursively walk through the table to find the transitive dependencies. This is largely based on how we handle subtarget features in the MC layer from the tablegen descriptions.