Evaluate influence of chunk size on downloads

[hagenw]

In the Artifactory and the Minio backends (#231 (review)), we use a chunk size of 4 kB during download:

audbackend/audbackend/core/backend/artifactory.py

Line 44 in 937da89

chunk: int = 4 * 1024,

We should check if this value has an influence of the download speed we can achieve.