HPCC-10311 Skip casts when deducing the names of implicit fields in records

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5707 from ghalliday/issue10311

HPCC-10311 Skip casts when deducing the names of implicit fields in records

Reviewed-By: Jamie Noss <james.noss@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>