C#: Restructure code prior move to .NET Core

The main focus here was to remove the majority of code that relied on
Mono's embedding APIs, specially the reflection APIs. The embedding
APIs we still use are the bare minimum we need for things to work.
A lot of code was moved to C#. We no longer deal with any managed
objects (`MonoObject*`, and such) in native code, and all marshaling
is done in C#.

The reason for restructuring the code and move away from embedding APIs
is that once we move to .NET Core, we will be limited by the much more
minimal .NET hosting.

PERFORMANCE REGRESSIONS
-----------------------

Some parts of the code were written with little to no concern about
performance. This includes code that calls into script methods and
accesses script fields, properties and events.
The reason for this is that all of that will be moved to source
generators, so any work prior to that would be a waste of time.

DISABLED FEATURES
-----------------

Some code was removed as it no longer makes sense (or won't make sense
in the future).
Other parts were commented out with `#if 0`s and TODO warnings because
it doesn't make much sense to work on them yet as those parts will
change heavily when we switch to .NET Core but also when we start
introducing source generators.
As such, the following features were disabled temporarily:
- Assembly-reloading (will be done with ALCs in .NET Core).
- Properties/fields exports and script method listing (will be
  handled by source generators in the future).
- Exception logging in the editor and stack info for errors.
- Exporting games.
- Building of C# projects. We no longer copy the Godot API assemblies
  to the project directory, so MSBuild won't be able to find them. The
  idea is to turn them into NuGet packages in the future, which could
  also be obtained from local NuGet sources during development.

1 files changed, 0 insertions, 52 deletions

diff --git a/modules/mono/mono_gd/gd_mono_header.h b/modules/mono/mono_gd/gd_mono_header.h
deleted file mode 100644
index bf21283080..0000000000
--- a/modules/mono/mono_gd/gd_mono_header.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/*************************************************************************/
-/*  gd_mono_header.h                                                     */
-/*************************************************************************/
-/*                       This file is part of:                           */
-/*                           GODOT ENGINE                                */
-/*                      https://godotengine.org                          */
-/*************************************************************************/
-/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
-/*                                                                       */
-/* Permission is hereby granted, free of charge, to any person obtaining */
-/* a copy of this software and associated documentation files (the       */
-/* "Software"), to deal in the Software without restriction, including   */
-/* without limitation the rights to use, copy, modify, merge, publish,   */
-/* distribute, sublicense, and/or sell copies of the Software, and to    */
-/* permit persons to whom the Software is furnished to do so, subject to */
-/* the following conditions:                                             */
-/*                                                                       */
-/* The above copyright notice and this permission notice shall be        */
-/* included in all copies or substantial portions of the Software.       */
-/*                                                                       */
-/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
-/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
-/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
-/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
-/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
-/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
-/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
-/*************************************************************************/
-
-#ifndef GD_MONO_HEADER_H
-#define GD_MONO_HEADER_H
-
-#include <cstdint>
-
-#ifdef WIN32
-#define GD_MONO_STDCALL __stdcall
-#else
-#define GD_MONO_STDCALL
-#endif
-
-class GDMonoAssembly;
-class GDMonoClass;
-class GDMonoField;
-class GDMonoMethod;
-class GDMonoProperty;
-
-class IMonoClassMember;
-
-#include "managed_type.h"
-
-#endif // GD_MONO_HEADER_H