csharp: Rename register_event_proxies.

Summary:
To better adhere to C# conventions and state it is for generated code
only.

Ref T7702

Reviewers: vitor.sousa, segfaultxavi

Reviewed By: segfaultxavi

Subscribers: cedric, reviewers, committers

Tags: efl

Maniphest Tasks: T7702

Differential Revision: https://phab.enlightenment.org/D8369