Convert vParquet5 service stats from map to list

[mdisibio]

What this PR does:
Small tweak to convert the service stats from map columns to list. Not critical but has a few benefits:

• sorted/more determinstic output - the maps were always iterated in random order so the service stats columns were unsorted, and it was impossible to build parquet files deterministicly
• fixed to add snappy/dict encoding. - Small reduction in file size and makes these columns viable for future fetch optimizations

Which issue(s) this PR fixes:
Fixes #

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]