Rethink what belongs in runtime/controllers

[hiddeco]

Historically, runtime/controllers used to facilitate setting up helpers (to e.g. initialize metrics in a common way for reconcilers to consume).

However, since growing it to support label selectors and rate limit flags. It has become an odd bag of mixed things (and not just "helpers"), which also has overlap with other sub-packages which provide component specific flags like runtime/leaderelection and runtime/client.

Given this, it looks like we need to rethink the structure and move, separate and/or divide (parts of it) to other places.