Refactor alliance benchmarks to v2 (#1868)
- This PR refactors `alliance/src/benchmarkings.rs` to use benchmarking v2. These changes are needed to improve the readability and maintainability of the benchmarking code. - No known issue to backlink. ## Local Testing 1. `cargo build --features runtime-benchmarks` 2. `cargo run --locked --release -p node-cli --bin substrate-node --features runtime-benchmarks -- benchmark pallet --execution wasm --wasm-execution compiled --chain dev --pallet "*" --extrinsic "*" --steps 2 --repeat 1`