Clean up gemini-3h compatibility code

[NingLin-P]

This is a tracking issue for cleaning up the gemini-3h compatibility code in main.

An incomplete list of things to clean up:

• Runtime API version check, search api_version throughout the codebase
• Domain inherent extrinsic order: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/domains/client/block-builder/src/lib.rs#L204
• chain_rewards field in the ER::block_fess: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/crates/sp-domains/src/lib.rs#L284-L285
• pallet-subspace-mmr digest: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/crates/pallet-subspace-mmr/src/lib.rs#L61
• Unused ProofOfElection::consensus_block_hash field: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/crates/sp-domains/src/lib.rs#L731
• Typo in is_domain_runtime_updraded_since: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/crates/sp-domains/src/lib.rs#L1505
• Deprecated fraud proof verification host function: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/crates/sp-domains-fraud-proof/src/runtime_interface.rs#L24
• Rename field Operator::status to Operator::_status: https://github.com/subspace/subspace/blob/69dda1652c1537b78dc4e47c6bc415d6e9f858a4/crates/pallet-domains/src/staking.rs#L193

cc @nazar-pc @vedhavyas feel free to add anything I missed.

[nazar-pc]

For my changes one would simply have to go through TODOs. Every single thing I could think of I create a TODO for.