Optional use of an external zlib

Resurrected external zlib branch based on @duncanmmacleod work. The main fix is about an incorrect mapping to uncompress2 instead of uncompress.

I have tested it with a FdIOServer instance, which seems to work fine. Regarding the performance, it seems there is no difference between the internal zlib and the external one from AlmaLinux9.

I have quickly tried to use zlib-ng (branch wip/external-zlib-ng). It seems there is a big impact on performance (30% less CPU running a FdIOServer test). To be confirmed using valgrind.