CI: Add 4.2-stable.expected file for GDExtension compatibility checks

[akien-mga]

Adds the editor hint for --validate-extension-api to match --dump-extension-api, otherwise we're missing the EditorInterface singleton.

[AThousandShips]

Should the 4.1 file be renamed like the 4.0 one was?

[akien-mga]

We have the following errors:

2023-12-04 16:18:27 URL:https://raw.githubusercontent.com/godotengine/godot-cpp/godot-4.2-stable/gdextension/extension_api.json [5501700/5501700] -> "/tmp/tmp.WdNiCBDP1l" [1]
Godot Engine v4.3.dev.mono.custom_build.156b07f14 - https://godotengine.org/
 
Error: Validate extension JSON: API was removed: singletons/EditorInterface

2023-12-04 16:18:27 URL:https://raw.githubusercontent.com/godotengine/godot-cpp/godot-4.0-stable/gdextension/extension_api.json [5175722/5175722] -> "/tmp/tmp.EoFQLdx9mx" [1]
Godot Engine v4.3.dev.mono.custom_build.156b07f14 - https://godotengine.org/
 
ERROR: New API lacks base array: enums
   at: compare_dict_array (core/extension/extension_api_dump.cpp:1350)
2023-12-04 16:18:28 URL:https://raw.githubusercontent.com/godotengine/godot-cpp/godot-4.1-stable/gdextension/extension_api.json [5318978/5318978] -> "/tmp/tmp.MBIcrUqT41" [1]
Godot Engine v4.3.dev.mono.custom_build.156b07f14 - https://godotengine.org/
 
ERROR: New API lacks base array: enums
   at: compare_dict_array (core/extension/extension_api_dump.cpp:1350)

The New API lacks base array: enums errors are also reproducible in the current master branch, and don't seem to mark the check as failed.

API was removed: singletons/EditorInterface is new from adding the 4.2-stable file though. From a quick look I don't understand why it's raised. Both the 4.2-stable and the API json generated by my local build have that entry, yet I get this error.

CC @RedworkDE

[AThousandShips]

Could it be related in some way to that the version tag is updated after that? The .json file in godot-cpp (for the master branch) is from the 4.2 branch pre updating to 4.3-dev, unsure if it is used in the comparison for this

The relevant file in godot-4.1-stable on godot-cpp is for version 4.1, so that's a point of difference

[akien-mga]

The script downloads the json from the godot-cpp tag of the version in the filename (first one if it's a range), so it should be comparing 4.3-dev (this PR) with 4.2-stable.
https://github.com/godotengine/godot/blob/master/misc/scripts/validate_extension_api.sh#L58-L61

[akien-mga]

This fixes the issue that singletons/EditorInterface was missing in the API generated by --validation-extension-api, thus failing the comparison with the file generated by --dump-extension-api, which uses editor hint.

The rest is just a cosmetic change to keep GDExtension stuff visually grouped together.

[aaronfranke]

The text at this file should be changed to be in sync with the 4.0->4.1 file. I updated #76560 to include this.