feat: redis data source C bindings

[cwaldren-ld]

This adds C bindings for creating a Redis Source, as well as a LazyLoad config method to accept pointers to the C type representing an instantiated Redis Source.

Demo:

LDServerLazyLoadBuilder lazy_builder = LDServerLazyLoadBuilder_New();

struct LDServerLazyLoadRedisResult out_result;
if (!LDServerLazyLoadRedisSource_New(uri, prefix, &out_result))
     printf("%s\n", out_result.error_message);
     exit(1);
}

LDServerLazyLoadBuilder_SourcePtr(lazy_builder, out_result.source);

LDServerConfigBuilder_DataSystem_LazyLoad(cfg_builder, lazy_builder);

[shortcut-integration[bot]]

This pull request has been linked to Shortcut Story #225989: C bindings for redis data source.