Remove duplicate support for QUERY_BATCH_SIZE

Related to #340656 (closed)

Note: Currently targeting branch 357230-deprecate-old-migrations - will target master once blocking MR is merged.

All existing Advanced Search migrations that used the old style constant definition of QUERY_BATCH_SIZE will be deprecated in %15.0. We can also remove support for this in the code and will only support the migration option batch_size.