Is your feature request related to a problem? Please describe.
For historical reasons, currently all chunks for all segments in stream are stored in single directory. This is not scalable.

Describe the solution you'd like
Each segment should have separate directory under which the chunks for that segments are stored.
This can be achieved by simply changing the format string for generating chunk name
Here we just fix this for any new segments only.

Describe alternatives you've considered
Current solution is not scalable.

Additional context
Add any other context or screenshots about the feature request here.