This is second of three big naming convention changes. In this commit,
we change the naming conventions for hook functions and variable
functions:
1. Replace the bar | to indicate a hook function with a -h suffix, e.g.
doom|init-ui -> doom-init-ui-h
doom|run-local-var-hooks -> doom-run-local-var-hooks-h
2. And add a -fn suffix for functions meant to be set on variables,
e.g.
(setq magit-display-buffer-function #'+magit-display-buffer-fn)
See ccf327f8 for the reasoning behind these changes.
