Harmonize function parameter names for Postgres 18.

Harmonize function parameter names for Postgres 18.

Make sure that function declarations use names that exactly match the
corresponding names from function definitions in a few places.  These
inconsistencies were all introduced during Postgres 18 development.

This commit was written with help from clang-tidy, by mechanically
applying the same rules as similar clean-up commits (the earliest such
commit was commit 035ce1fe).