Split the "Importing 3D scenes" article into multiple pages

[aaronfranke]

I was planning to add some more content to this article, but I noticed the article was getting super long and hard to navigate. This PR splits up this documentation article into 4 pages (plus an index page):

• available_formats: Describes the available 3D formats and how to use them.
• model_export_considerations: Describes conventions and best practices for exporting 3D models from Blender/etc.
• node_type_customization: Describes how to customize node types using node name suffixes.
  • Note: The file name is purposefully a bit generic, because I want to expand this in the future with information about how to use glTF extensions to customize node types, in addition to node name suffixes.
• import_configuration: Describes customizing the imported scene without modifying the file being imported.

The contents of these articles are exactly the same as the old unified article, the only difference in content is that I added some text to the headers of some of these files. I've collapsed them in the details below:

Added to index.rst:

Importing 3D scenes
===================

Godot supports importing 3D scenes from various file formats.
This documentation section describes what those formats are, and how to use
them, including exporting with the correct conventions and best practices,
and how to customize the node type using a suffix in the node name.
The import configuration article describes how to customize the
imported data using the import dock, the advanced import settings
dialog, and inherited scenes.

Added to model_export_considerations.rst:

Model export considerations
===========================

Before exporting a 3D model from a 3D modeling application, such as Blender,
there are some considerations that should be taken into account to ensure that
the model follows the conventions and best practices for Godot.

Added to import_configuration.rst:

Import configuration
====================

Godot provides several ways to customize the imported data, such as the
import dock, the advanced import setting dialog, and inherited scenes.
This can be used to make further changes to the imported scene, such
as adjusting meshes, adding physics information, and adding new nodes.
You can also write a script that runs code at the end of the import
process to perform arbitrary customization.

Note that, when applicable, modifying the original data should be preferred
to configuring the scene after import. This helps minimize the differences
between the 3D modeling application and the imported scene. See the
:ref:`doc_importing_3d_scenes_model_export_considerations` and
:ref:`doc_importing_3d_scenes_node_type_customization` articles
for more information.

Note: I'm still kind of a reStructured Text noob. I tried to structure it similar to other documentation, specifically using the ESCN importer code as an example. I also included a redirect.

[fire]

DAE (COLLADA), an older format that is fully supported.

There are open bugs regarding skeleton import, but we aren't able to deprecate Collada importer.

[aaronfranke]

That's the exact same text as currently in the docs.

[lyuma]

COLLADA is basically deprecated and has known issues, so support is poor. I would at a minimum remove the word "fully" since it is certainly not fully supported,
The biggest support issue is that skinned meshes are currently completely broken. See #68410.

[fire]

/home/runner/work/godot-docs/godot-docs/classes/class_resourceimporterobj.rst:31:unknown document: ../tutorials/assets_pipeline/importing_scenes

Some cicd errors.

[aaronfranke]

@fire CICD errors need godotengine/godot#80872 EDIT: Updated this PR with those changes.

[lyuma]

rename tutorials/assets_pipeline/{importing_scenes.rst => importing_3d_scenes/import_configuration.rst} (59%)

Renaming a documentation will cause a 404 error for all existing links to that page. It is good practice to add a redirect from the old page to the new one.

EDIT: I missed it but redirects.csv has the correct redirect already configured. It looks good!

There was one mistake with the seealso for FBX landing on the wrong page, but other than that it looks correct technically speaking.

I don't think we should act on changes to the text of the documentation. I was just replying to the thing fire noticed, and I noticed something thing about glb embedded but we can fix it in a separate PR.

[lyuma]

COLLADA is basically deprecated and has known issues, so support is poor. I would at a minimum remove the word "fully" since it is certainly not fully supported,
The biggest support issue is that skinned meshes are currently completely broken. See #68410.

[lyuma]

Looks good! I see the redirect in redirects.csv so it should work.

[adamscott]

@akien-mga @YuriSizov
To merge with godotengine/godot#80872

[Scoppio]

Good split.

[skyace65]

Did I miss a change recently? I thought we weren't supposed to update class reference pages in the docs repository.

[aaronfranke]

@skyace65 An identical change has been made on the main repo. godotengine/godot#80872

This is the only way to do it. It's a mid-air conflict with the main repo referencing the docs.

[skyace65]

Only issues I could find with this. Everything else looks perfect.

[skyace65]

Thanks! I merged the PR in the engine repository as well.