Add missing ImGui.TableGetSortSpecs API (and related objects)

[ultraq]

Description

This PR adds the missing binding for the ImGui::TableGetSortSpecs API, which includes structs to describe table and column sorting with ImGuiTableSortSpecs and ImGuiTableColumnSortSpecs respectively.

I had a workaround for the missing binding for a prior version which I posted about in #114, but with the recent release and seeing the binding generator being merged to main, I thought I'd try to understand the generator work and complete the API properly. I still had to write some custom JNI code for ImGuiTableSortSpecs.Specs which holds a ImGuiTableColumnSortSpecs array as I couldn't find anything yet built to handle object arrays that weren't the ImVec types. (Happy to be proven wrong on that point though!)

I also added a commit to add a binding for an ImGui::TreeNodeEx overload which seems to have gone missing with the generator work (maybe? 🤷‍♂️) and that I happen to be using in a project that I used to test these changes.

Type of change

• Minor changes or tweaks (quality of life stuff)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

[SpaiR]

This looks great! I'm really pleased to see such a quick adaptation and usage of the new API (even without documentation 🫠).

As for the code itself - I don't have any issues with it; everything seems to be in order at first glance. Writing your own JNI is perfectly normal. Auto-generation currently (hopefully only for now) doesn't cover such scenarios, so the main thing is that it works.

However, there's one last step you need to complete - to generate the API itself 🙃. This is precisely where documentation would be helpful, but all generated API code should be committed to the repository along with the rest of the code. So, you need to run the command ./gradlew :imgui-binding:generateApi, which will generate the corresponding code in the generated folder. The content of the generated folder should not be modified, but if something doesn't seem alright - definitions or generator code can be adjusted. (At least, that is the point right now.)

[ultraq]

Cool, I was running that step to get an artifact to test with but didn't know what the story was with built/generated files. Thanks for pointing that out - I'll get it sorted shortly!