Expose EditorExport through the EditorInterface singleton

[allenwp]

Exposes EditorExport through the EditorInterface singleton. Also exposes functions relating to feature tags of platforms and presets, similar to the existing EditorExportPreset.get_custom_features() function.

Background
Many properties of EditorExportPlatform EditorExportPreset and have been exposed in #90782, but it is currently not possible to iterate through these in some types of editor plugins and tools. Many of the newly exposed properties could be used in editor tools, such as my Resource Remaps plugin, which loads custom and platform feature tags.

Related PRs
Feature tags in scripting: #86747

Implementation
I have kept the scripting API similar to the C++ API, but that does mean there are some style differences between getting custom features (existing function that returns a comma delimited String) and getting the platform/preset features (new functions that return a TypedArray<String>).

[groud]

The feature looks quite interesting to me, but for our use case, we would have liked to be able to add a new export preset too. We are working on the editor plugin for a specific platform that requires specific parameters in the export menu, so it would have been great if we were able to create this preset automatically, instead of requiring the users to create the preset themselves.

[allenwp]

The feature looks quite interesting to me, but for our use case, we would have liked to be able to add a new export preset too. We are working on the editor plugin for a specific platform that requires specific parameters in the export menu, so it would have been great if we were able to create this preset automatically, instead of requiring the users to create the preset themselves.

You're welcome to use this PR as a starting point for the functions you need!

The documentation is what I spent the most time on with this PR, so please feel free to grab that if you use any of this. The rest is pretty mindless exposing of existing functions to the ClassDB

[citizenll]

I think this feature is very useful. In addition, more set methods should be exported in the preset; currently, only the get methods have been exported(I am currently creating custom pck subpackages by modifying the preset).