Add tests for all cases where OOM is expected

We should add tests for most or all of the subtasks of IMPALA-4834 that exercise the expected OOM code path. I'll add some bullet points here to track what the coverage is and what's missing.

• Aggregations with large var-len string expressions
• Top-N with large window
• Kudu scans : covered by kudu-scan-mem-usage.test
• Nested loop join : covered by single-node-nlj-exhaustive.test
• Many duplicate keys on build side of hash join
• Large number of NULLS on build side of NAAJ : covered by spilling-naaj-no-deny-reservation.test
• HDFS table partitioned insert : covered insert-mem-limit.test
• Large analytic window can't be spilled
• Queries processing large strings (may need multiple tests to cover different places). large_strings.test has some coverage
• Parquet files with large pages
• Exchange uses a lot of memory