Testnet Release v0.4.0

What's Changed

• Limit gas to 3500 by @nxqbao in #127
• Implement function emergency exit for Validators by @ducthotran2010 in #126
• [ValidatorSet] Replace error messages by custom erorrs by @nxqbao in #129
• [RoninGovernanceAdmin] Expose function & store bridge operator set by @ducthotran2010 in #132
• [ValidatorSet] Add details for StakingRewardDistributed event by @nxqbao in #133
• Impl forwarder contract by @nxqbao in #128
• Support voting without signatures on the Ronin network by @ducthotran2010 in #130
• [Staking] Rename for clarity between pools and active pools by @nxqbao in #134
• v0.4.0 by @nxqbao in #135
• Add deployment artifacts for v0.4.0 by @minh-bq in #139

Full Changelog: v0.3.2...v0.4.0