Prop 47: Software Upgrade v21

The Xion v21 (https://github.com/burnt-labs/xion/releases/tag/v21.0.0) software upgrade introduces significant improvements to WebAuthn functionality, CosmWasm updates, and various bug fixes and enhancements. KEY FEATURES: * WebAuthn Improvements - Comprehensive fixes to WebAuthn functionality, improved block timestamp handling, updated to latest go-webauthn library * CosmWasm v0.61.x Upgrade - Enhanced smart contract execution capabilities and performance improvements * Fee Abstraction Codec - Restored fee abstraction codec registration for improved fee handling * Code Quality & Testing - Added comprehensive unit tests including JWK unit tests, updated test setup functions * Bug Fixes & Cleanup - Removed unused migration code, fixed upgrade name issues * Contributors: edjroz, Peartes, 2xburnt. This upgrade is scheduled for block height 12,690,000 via governance proposal #046. Release Notes: https://github.com/burnt-labs/xion-mainnet-1/blob/main/release_notes/v21.md * Full Changelog: https://github.com/burnt-labs/xion/compare/v20.0.0...v21.0.0