[.NET] Replace Reflection-Based implementation with Generated one in CreateManagedForGodotObjectBinding

[Delsin-Yu]

Before this PR, ScriptManagerBridge used reflection-based implementation to instantiate engine wrapper types; this PR introduces a generated Constructors class to store all constructor calls inside a dictionary and invoke them with nativeTypeNameStr as key.

A new internal constructor was added to the GodotObject class that accepts IntPtr to avoid the FormatterServices.GetUninitializedObject call.

[raulsntos]

Thank you so much, this looks great! I haven't been able to test it very thoroughly yet, but so far it doesn't seem to break anything.

[Delsin-Yu]

What?

[raulsntos]

Looks good to me and seems to work fine in my testing, although I'm always wary of changes to the script bridge so more testing is always welcome.

[Delsin-Yu]

I'm currently testing it with our in-development game; once I identify any issues, I will push follow-up fixes (if not merged) or open a new PR (if merged).

[AThousandShips]

Please edit your commit message to remove unnecessary information, just keeping the title itself, the individual squashed steps are not necessary

[akien-mga]

Thanks!