Nimbus consensus client hits stable ground with crucial v26 2 fix release

Nimbus consensus client v26.2.0 released with improved network stability fixes. Addresses mainnet block rejection scenario caused by cache corruption in Merkle tree hashing, averted since restart only. Fixes include simplified era file-based node startup, hash_tree_root cache invalidation for SSZ Lists. Update urged due to medium urgency. SHA512 checksums provided for Linux AMD64, ARM64, ARM, and Windows AMD64, macOS ARM64 versions.