Current release: generated code variables collision (possible regression)

Between release (25.9.23) and current release (25.12.19) I stopped being able to compile my flatbuffers into C/C++ headers, so I count it as possible regression. I use Gentoo, and current release appeared in stable packages recently, therefore I had not noticed before.

geometry.fbs
```
namespace flatbuff;
namespace flatbuff.twm;
table D3_t {
x:int;
y:int;
z:int;
}
table track_line_t {
A:twm.D3_t;
B:twm.D3_t;
}

namespace flatbuff.twm.wrappers_geometry_t;
table dummy {
val:byte;
}

namespace flatbuff.twm;
union geometry_t {
dummy:wrappers_geometry_t.dummy,
line:twm.track_line_t,
}

namespace flatbuff;
```

```
$ flatc --cpp geometry.fbs

warning:
/tmp/geometry.fbs:10: 5: warning: field names should be lowercase snake_case, got: A
/tmp/geometry.fbs:11: 5: warning: field names should be lowercase snake_case, got: B
```

(It was legacy code that was converted to flatbuffers, so that's why snake_case had not been used and original field names were kept instead. Hence the warning.)

```
$ cat geometry_generated.h
...
struct track_line_t FLATBUFFERS_FINAL_CLASS : private ::flatbuffers::Table {
...
template
bool Verify(::flatbuffers::VerifierTemplate &verifier) const {
return VerifyTableStart(verifier) &&
VerifyOffset(verifier, VT_A) &&
verifier.VerifyTable(A()) &&
VerifyOffset(verifier, VT_B) &&
verifier.VerifyTable(B()) &&
verifier.EndTable();
}
};
...
```

As stated above, with previous versions of flatbuffers it worked.