HPCC-8289 - Use allocator caching

Use row allocator caching mechanism (see HPCC-8278)

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #3882 from jakesmith/hpcc-8289

HPCC-8289 - Use allocator caching

Reviewed-By: Gavin Halliday <gavin.halliday@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>