Further optimizations for get_delta_stats with Ray

[rkenmi]

deltacat/deltacat/compute/stats/utils/io.py

Lines 103 to 104 in 18c6c5f

	for file_idx, manifest in enumerate(delta.manifest.entries):
	entry_pyarrow_table: LocalTable = deltacat_storage.download_delta_manifest_entry(delta, file_idx)

A single Ray task sequentially downloading delta manifests with a large number of manifest entries may take more time to complete, as opposed to having a single Ray task handle the download for a specific manifest entry by file index.