Support for implementing digest Module type callback using existing Module APIs

[KarthikSubbarao]

The Module data types provide a callback for digest and this is called when the DEBUG command is used on the module object for developing and testing for correctness. For modules to implement the digest callback, we will need wrapper functions in the valkeymodule-rs SDK written around the following existing Module APIs:

ValkeyModule_DigestAddStringBuffer
ValkeyModule_DigestAddLongLong
ValkeyModule_DigestEndSequence
ValkeyModule_GetKeyNameFromDigest
ValkeyModule_GetDbIdFromDigest

Example Valkey Module in C implementing the digest callback: https://github.com/valkey-io/valkey/blob/unstable/tests/modules/datatype2.c#L614-L634

[hahnandrew]

Hey @KarthikSubbarao, happy to pick this up 🙂