When a Reference managed instance is garbage collected and its finalizer is called, it could happen that the native instance is referenced once again before the finalizer can unreference and memdelete it. The workaround is to create a new managed instance when this happens (at least for now).
First of all, this fixes the handling of exceptions so the engine actually notices them,
it was broken in 4172fa03b5.
Next, unhandled exceptions now do NOT cause an abort(). They're logged now,
so before #16987. The pending exception thing still works though.
- Sometimes `StackFrame.GetMethod()` returns null (e.g.: latest frame of a `MissingMethodException`). Still not sure what to do with that frame (maybe skip it), but at least it no longer fails.
- Skip `CSharpLanguage::debug_get_current_stack_info()` if an error is printed from `GDMonoUtils::update_corlib_cache()`.
- Fix crash when calling `GDMonoUtils::print_unhandled_exception(exc)` if there is no ScriptDebugger attached.
Using `misc/scripts/fix_headers.py` on all Godot files.
Some missing header guards were added, and the header inclusion order
was fixed in the Bullet module.
- Allow non-public fields to be exported as well (to avoid confusion).
- Set PROPERTY_HINT_RESOURCE_TYPE for resource derived fields.
- Support enums and automatically fill PROPERTY_HINT_ENUM's hint_string for enum fields.
