Update UE-side plugin to build against current ue5-main branch

[mattyjams]

This should also enable building the UE plugin for 5.4.

Most of the changes are simply to add missing includes of header files. The last few releases of UE have been getting better about stripping out unused headers to improve compile times, so some that may have been getting included indirectly may not be any longer.

Other smaller changes of note:

• Specify the underlying type of Blueprint enums to squelch warnings
• Provide default values for exposed numerical properties in Blueprint types and USTRUCTs to squelch warnings
• Declare and define templated Utils functions in the header file
• Address a deprecation where as of UE 5.3, FAssetEditorToolkit::CloseWindow() should be provided a reason argument (https://github.com/EpicGames/UnrealEngine/commit/31830290abdf11c3bad9dfee1e88a0cea47e562b)