[zero] add chunk size search for chunk manager

[ver217]

Add chunk size search:

def search_chunk_size(module: torch.nn.Module,
                      search_range: int,
                      n_grids: int,
                      min_chunk_size: Optional[int] = None) -> int:
    pass

Apply grid search in [min_chunk_size, min_chunk_size+search_range]. If min_chunk_size=None, it's set to the number of elements of the largest parameter.

Usage:

best_chunk_size = ChunkManager.search_chunk_size(model, 128 * 1024**2, 4)