Easier way to know when tile bvh query has finished

[nvtw]

Description

Introduce something like wp.tile_query_valid(query which simplifies using tile bvh queries.

Context

The wp.tile_max below is a bit wasteful

# Before
result_tile = wp.tile_bvh_query_next(query)
while wp.tile_max(result_tile)[0] >= 0:
    result_idx = wp.untile(result_tile)
    if result_idx >= 0:
        ...
    result_tile = wp.tile_bvh_query_next(query)

# After
while wp.tile_query_valid(query):
    result_tile = wp.tile_bvh_query_next(query)
    result_idx = wp.untile(result_tile)
    if result_idx >= 0: