Add sorted voter list preserve mechanism to multi-block staking pallet #6560

Job	Run time
preflight / preflight	42s
preflight / ci-versions	1m 6s
test-frame-ui	5m 28s
test-full-crypto-feature	2m 56s
cargo-check-benches (master)	4m 53s
cargo-check-benches (current)	4m 47s
cargo-check-each-crate (1)	4m 37s
cargo-check-each-crate (2)	4m 35s
cargo-check-each-crate (3)	4m 22s
cargo-check-each-crate (4)	4m 17s
cargo-check-all-crate-macos	6m 15s
cargo-check-each-crate (5)	4m 14s
cargo-check-each-crate (6)	3m 52s
cargo-check-each-crate (7)	3m 45s
test-node-metrics	4m 26s
test-frame-examples-compile-to-wasm	2m 27s
node-bench-regression-guard	6s
test-deterministic-wasm	1s
check-tracing	1s
check-metadata-hash	1s
All test misc tests passed	1s
	1h 2m 52s

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