[CPP] New marshalling extern api errors are shown in the std files rather than the source

I have the following error:
```hx
[ERROR] /home/j/Documents/Projects/simple/SimpleChartDev/haxe_modules/linc_skia/skia/SkSpan.hx:7: lines 7-11

7 | extern class SkSpan {
- | [...]
11 | }
|
| CPP0003: Invalid parameter for a marshalling type
```
The code in this file is
```hx
@:semantics(value)
@:cpp.ValueType
extern class SkSpan {
public function new(ptr:Star, size:Int):Void;
public function size():Int;
public function empty():Bool;
}
```
But the error should point to where I'm using this incorrectly rather than the source file, I think this is an issue for other error codes as well

Reproduce the diagnostic using the SkSpan.hx example at line 7 and inspect how CPP0003 is reported for the extern declaration. Trace the marshalling validation to determine where the incorrect usage is known, then verify that the error points to that usage rather than the std file and check whether related error codes behave consistently.

Written by the indexing model from the issue text.