Spider patches 026 (MDEV-7723), 031 (MDEV-7727) and 058 (MDEV-12532)

This allows the storage engine to internally compute sum and count
operations.

- Enhance sum items to be able to store the sum value directly.
- return_record_by_parent() is enabled in spider as
  HANDLER_HAS_DIRECT_AGGREGATE is defined
- Added spd_environ.h to spider. This is loaded first to ensure that all
  MariaDB specific defines that are used by include files are properly
  defined.
- This code is tested by the existing spider tests direct_aggregate.test
  and direct_aggregate_part.test and also partition.test