feat: demonstrate issue with partial aggregation

[ariel-miculas]

Related to #22526

[ariel-miculas]

$ cargo test -p datafusion-physical-plan test_partial_agg_batch_memory_size_is_bounded
    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.17s
     Running unittests src/lib.rs (target/debug/deps/datafusion_physical_plan-e508c50bdaa05029)

running 1 test
test aggregates::row_hash::tests::test_partial_agg_batch_memory_size_is_bounded ... FAILED

failures:

---- aggregates::row_hash::tests::test_partial_agg_batch_memory_size_is_bounded stdout ----

thread 'aggregates::row_hash::tests::test_partial_agg_batch_memory_size_is_bounded' (2039740) panicked at datafusion/physical-plan/src/aggregates/row_hash.rs:1903:13:
emitted batch has 294912 bytes, expected ≤ 49152 (batch_size=1024, rows=1024)
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    aggregates::row_hash::tests::test_partial_agg_batch_memory_size_is_bounded

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 1435 filtered out; finished in 0.01s

error: test failed, to rerun pass `-p datafusion-physical-plan --lib`