efl_mono: remove '_' from type for C# naming convention

efl_mono: remove '_' from type for C# naming convention

Summary:
"type" in .eo is converted to "struct" in .eo.cs.
Since the type name in .eo is the same with the struct name .eo.cs,
'_' is removed from the converted struct in .eo.cs for C# naming
convention.

For example, Efl.Callback_Priority is defined in efl_object.eo and
the name is converted to Efl.CallbackPriority in efl_object.eo.cs.

Efl.Access.StateSet in workaround.cs causes duplicated definition
with this patch so Efl.Access.StateSet in workaround.cs is removed.

Test Plan: Compile with autogen.sh --enable-csharp-bindings

Reviewers: lauromoura, segfaultxavi, felipealmeida

Reviewed By: felipealmeida

Subscribers: segfaultxavi, cedric, #reviewers, #committers, woohyun

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7597