Please error, or at least warn, when a managed type is included in INetworkSerializeByMemcpy

Is your feature request related to a problem? Please describe.

My coworker was unfamiliar with INetworkSerializeByMemcpy and the FixedStringNNNBytes types, and added a string field to an existing INetworkSerializeByMemcpy struct. This caused me great headaches (it made it into a publicly released patch), trying to track down segfault heap corruption that only showed up in very specific multiplayer circumstances (the string was normally null, which probably masked the issue).

Describe the solution you'd like

Please cause a build error when a managed type (a class, a string, or the like) is included in an INetworkSerializeByMemcpy type. I cannot think of any use case where it would be valid or intended to serialize a managed GC pointer by memcpy. At least a warning if nothing else.

It doesn't have to be perfect, even just checking for string would be lovely - string specifically is such a massive footgun, it's so easy to accidentally include and think it'll work fine. The fact it crashes later on via unrelated segfault heap corruption bringing down the editor, instead of a C# Exception, is especially rough.

Comienza localizando la definición de INetworkSerializeByMemcpy y sus pruebas de validación o serialización. Traza cómo se comprueban los tipos que lo implementan durante la compilación o en tiempo de ejecución y, después, añade cobertura para campos de tipo string y otros campos administrados; se considerará terminado cuando dichos tipos produzcan un error o una advertencia de compilación en lugar de una serialización insegura mediante memcpy.