Inline and remove `process_predicate`.
Inline and remove `process_predicate`.

Because it has a single callsite.

This patch is large but trivial, doing the minimal amount of work
(mostly `self.` insertions) necessary.

aidancully/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust