Flink 1.20 Adds Significant Improvements Along w/Deprecations

Flink 1.20 introduces the DISTRIBUTED BY clause (FLIP-376) for unified bucketing strategies in Flink SQL, replacing connector-specific syntax. It also adds MATERIALIZED tables (FLIP-435) to manage data freshness requirements directly within Flink, deciding between streaming or batch refresh modes based on configuration. The DataStream API now supports parallel aggregations on non-keyed streams in batch mode (FLIP-380). Operational improvements include unified file merging for checkpoints (FLIP-306) to reduce blob storage load and costs, and enhanced recovery for batch jobs from JobMaster failures (FLIP-383). Legacy SinkFunction API and other configuration options are deprecated in preparation for Flink 2.0.