[Chapel Merge] Fix broken `--incremental` compilation under C backend

Branch: refs/heads/main
Revision: a9ecd8affcd663ee9951f2ef9e17830d13e81cfe
Author: dlongnecke-cray
Link: Fix broken `--incremental` compilation under C backend by dlongnecke-cray · Pull Request #29349 · chapel-lang/chapel · GitHub
Log Message:
Fix broken --incremental compilation under C backend (#29349)

I removed chplcgfns.h but didn't add a declaration for
chpl_global_serialize_table to a program-only header which exists to
keep --incremental compilation from breaking.

Reviewed by @jabraham17. Thanks!

Compare: Comparing 91bbe9b47d836d29c9d48e44230047f68fa317cb...19e1860d30c7e95a3deead2c9223343f5a7748c6 · chapel-lang/chapel · GitHub

Diff:
M runtime/include/chpl-prginfo-program-only-decls.h
https://github.com/chapel-lang/chapel/pull/29349.diff