@CXXSuperTemplate doens't work if the super class is placed in another file

For class

```java
@FFITypeAlias("arrow::Result")
@FFIGen(templates = @CXXTemplate(cxx = "int", java = "Integer"))
@CXXSuperTemplate(
type = "arrow.EqualityComparable",
template = @CXXTemplate(java = "arrow.Result", cxx = "arrow::Result")
)
@CXXHead(
system = "arrow/result.h"
)
public interface Result extends EqualityComparable>, CXXPointer {
}
```

and class

```java
@FFITypeAlias("arrow::util::EqualityComparable")
@FFIGen
@CXXHead(
system = "arrow/util/compare.h"
)
public interface EqualityComparable extends CXXPointer
{
}
```

The `CXXSuperTemplate` doesn't work if they are placed in different java files, but works if been placed in the the file.

Start by reproducing the example with Result and EqualityComparable in separate Java files, then trace how CXXSuperTemplate processes those two interfaces. Done means the annotation works across separate files as well as when both interfaces share one file.

Written by the indexing model from the issue text.