Add Cargo Feature to Use zlib-rs (instead of system zlib)

[redfire75369]

As of FF 137, zlib-rs is supported. By adding a feature flag for zlib-rs, it would reduce the amount of C compiled, and would reduce the number of system dependencies.

The USE_LIBZ_RS environment variable would be required, along with the libz-rs-sys crate (w/ the export-symbols feature). In theory, the zlib.h header should work, and cargo/linker should handle the rest. Given that zlib-rs doesn't provide headers, I'm not sure where we should get them from.