JS Flight/Barrage Refactor follow up

[niloc132]

This ticket documents known followup items from #5890. To expedite that PR, scope was reduced, and these details from #188 and related tickets still need to be resolved.

• JS ChartData type doesn't handle shifts correctly #2435
• JS API returns undefined for null string values #1917
• Display Unique Values in Column Statistics #5031
• Snapshot messages over 100MB throw in JS API #4563
• Web UI becomes frozen #3941
• DoPut (and eventually Publish) should also be handled using JVM classes (ChunkInputStreamGenerator types). See also Web UI CSV Upload followup #1041
• Plotting should support local dates/times #2419
• Subscriptions cannot change update interval
• Start using "columns as list" barrage option
• Verify logic around raced viewports, see if we need a better way to coalesce these updates/events
• Propose chunk api for efficient column reading
• Finish removing old/deprecated format apis

Preview-specific tasks:

• JS API exposes un-previewed tables to the UI in some cases, causing errors on subscribe #5708
• JSAPI support for fetching full array from an array preview column #2102
• JS API Pass the "original" type as another param when column is converted to preview #3358
• Web UI becomes frozen #3941