Update bundled PostgreSQL static libraries to 18.4

[ProjectSky]

• update the bundled PostgreSQL/libpq headers and static libraries to 18.4 (resolve [PostgreSQL] Database error SCRAM authentication requires libpq version 10 or above #1802)
• adjust pgsql extension link inputs for the newer libpq split libraries, and drop unsupported macOS pgsql builds
• build connection parameters with instead of manually formatting a connection string
• make own and clear its , preventing leaks when prepared statements are executed repeatedly
• close prepared statements with when statement handles are destroyed
• track copied vs borrowed prepared-statement parameter buffers so borrowed strings/blobs are not freed (resolve [PostgreSQL] delete DBStatement cause server crash #1946)

[psychonic]

Thanks for doing this!

For security reasons, we don't allow external contributors to submit precompiled binaries, so I'll rebuild the libraries and push over top of these ones before merge. (Your build-postgresql-library project should make that trivial, so thank you for that as well). I'll also use our Linux build container for that so that we don't accidentally raise our minimum glibc version requirement.

[ProjectSky]

Totally understand. Glad the build project helped. Let me know if any further changes are needed on my end