Harmonize heapam and tableam parameter names.

Harmonize heapam and tableam parameter names.

Make sure that function declarations use names that exactly match the
corresponding names from function definitions.  Having parameter names
that are reliably consistent in this way will make it easier to reason
about groups of related C functions from the same translation unit as a
module.  It will also make certain refactoring tasks easier.

Like other recent commits that cleaned up function parameter names, this
commit was written with help from clang-tidy.  Later commits will do the
same for other parts of the codebase.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAH2-WznJt9CMM9KJTMjJh_zbL5hD9oX44qdJ4aqZtjFi-zA3Tg@mail.gmail.com