HPCC-8808 Fix issues with truncation of lookup values

Refactor the dictionary lookup code so that the search rows use full precision
fields, to avoid false positives when the search keys are larger than the
range that can be represented by the key fields.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
HPCC-8808 Fix issues with truncation of lookup values

Minor changes following code review.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #3969 from richardkchapman/dict-field-2

HPCC-8808 Fix issues with truncation of lookup values

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>