remove long-deprecated altbn128 library

[garyschulte]

The altbn128 library has been superseded by matterlabs for EIP-196 for years, and has been unused by besu since 2020

Now that matter-labs library is slated to be removed in favor of gnark-crypto and/or constantine implementations, it seems well overdue to remove this library from besu-native

• remove from gh workflows
• remove from build.sh
• remove from settings.gradle
• remove altbn128 directory altogether