[EPIC] A collection of Memory Accounting Limitations and Improvements

[alamb]

As DataFusion gets used more in production systems there is more of an interest in improving its memory accounting model. This epic lists related issues to try and get some organized discussion going

• Fix memory accounting in Datafusion #20714 from @cetra3
• [DISCUSSION] Memory accounting model discussion #16841 from @gabotechs
• NestedLoopJoinExec spill path: untracked allocation overshoots memory pool #22723 from @avantgardnerio
• GroupValuesRows::emit untracked decode buffer leaks past MemoryReservation #22739 from @avantgardnerio
• More accurate memory accounting in external sort #14748 from @2010YOUY01
• Downstream consumers of AggregateExec significantly overcount memory usage #22757 from @Samyak2
• Hash aggregation produces batches reporting huge memory size #22526 from @ariel-miculas
• Incorrect memory accounting in array_agg function #16517 from @sfluor