[BUG] Bad output indices from `pointcloud_search()` with batched shading

**Describe the bug**

When using `pointcloud_search()` with batched shader execution, the output `indices` array is not being filled correctly. It looks a little like OSL thinks the output is a uniform rather than a varying value, but I don't know enough about what is going on under the hood to be sure.

**OSL version and dependencies**

* OSL branch/version: 1.14.5.1
* OS: Rocky 8.8
* C++ compiler: GCC 11.2.1
* LLVM version: 15.0.7
* OIIO version: 3.0.6.1

**To Reproduce**

Steps to reproduce the behavior:

1. `oslc search.osl` (source code in section below).
2. `testshade -g 16 16 -batched -param file cloud.geo search.oso -o Cout batched.png`
3. `testshade -g 16 16 -param file cloud.geo search.oso -o Cout unbatched.png`
4. Compare `batched.png` to `unbatched.png`. The latter has the expected results, and the former does not.

In the above commands, `cloud.geo` is `testsuite/pointcloud-fold/cloud.geo` from the OSL repo.

**Evidence**

search.osl

```
shader search( string file = "", output color Cout = 0 )
{
int indices[1];

// Uncommenting this workaround gives the expected results in batched
// mode. I suspect it works by tricking OSL into realising that `indices`
// is a varying quantity.
// indices[0] = P[0];

if( pointcloud_search( file, P, 1, 1, "index", indices ) )
{
Cout = color( indices[0] / 15.0 );
}
else
{
Cout = color( 1, 0, 0 );
}
}
```

batched.png :

unbatched.png :

Esegui i comandi oslc e testshade elencati usando testsuite/pointcloud-fold/cloud.geo, quindi confronta l'output in batch con quello non in batch. Inizia dal punto di ingresso pointcloud_search e segui come viene gestito l'array degli indici di output durante l'esecuzione in batch. Il lavoro è completato quando batched.png corrisponde ai risultati non in batch attesi senza il workaround.

Scritto dal modello di indicizzazione a partire dal testo della issue.