libsecp256k1 v0.6.0 released

Among the key enhancements is the addition of a MuSig2 module, marking a significant advancement in the library's functionality. Furthermore, this version brings a more robust method for clearing secrets from the stack, ensuring enhanced security measures are in place. The removal of the unused secp256k1_scratch_space functions also simplifies the library, making it more efficient and streamlined for users. For those interested in exploring the full range of changes and updates made in this release, the complete changelog is available for review at the project's GitHub page. This update underscores the continuous efforts to improve and secure cryptographic practices within the Bitcoin development community.