Linking fails for Flax structs in c++

[z1dev]

Issue description:

I was trying to use TextRange and FontLineCache in Span<> array in a c++ plugin and this resulted in a linker error.

6>Fudgets.Bindings.Gen.obj : error LNK2001: unresolved external symbol "public: static struct ScriptingTypeInitializer TextRange::TypeInitializer" (?TypeInitializer@TextRange@@2UScriptingTypeInitializer@@A) 6>g:\projects\Flax\UIPluginTest\Plugins\Fudgets\Binaries\FudgetsEditorTarget\Windows\x64\Debug\Fudgets.dll : fatal error LNK1120: 1 unresolved externals

Adding the Render2D module to the .Build file(s) in my project didn't help. These structs don't have the FLAXENGINE_API in the engine source, so I added them. Doing that fixes the issue, but I don't know if that's the right solution.

Steps to reproduce:

Make some custom struct in a c++ project, and add for example API_FIELD() Span<TextRange> LineCache; and it will result in link error.

Minimal reproduction project:

Flax version:

1.7 latest master

[z1dev]

There are many other structs in Font.h without the FLAXENGINE_API too.

[mafiesto4]

Fixed in 5cada42.