efl-mono: Fix marshalling of struct in event data.

efl-mono: Fix marshalling of struct in event data.

Summary:
Previously, we just converted through PtrToStructure, which didn't have
the full marshalling info converting from the internal one to the
external.

This fixes the usage of the Efl.Loop.arguments event.

Also renamed the ToExternal methods to ToManaged, to make clearer that
the output struct is the one intended to be used from the managed code.

Also fixed a minor styling in the generated code (making it easier to be
inspected).

Depends on D7538

Reviewers: segfaultxavi, felipealmeida, bu5hm4n

Reviewed By: bu5hm4n

Subscribers: bu5hm4n, cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7539