Bug 1752444 - Part 2: Rewrite direct_call.py protocols to use...

Bug 1752444 - Part 2: Rewrite direct_call.py protocols to use {Parent,Child}Impl attributes, r=ipc-reviewers,media-playback-reviewers,alwu,mccr8

This is a mechanical change which was performed by a script based on the
contents of direct_call.py, and then manually checked over to fix
various rewriting bugs caused by my glorified sed script. See the
previous part for more context on the change.

Differential Revision: https://phabricator.services.mozilla.com/D137227