Fix/incorrect eras per cycle function

[Dinonard]

Pull Request Summary

Fix an issue where inflation recalculation era would be incorrectly calculated.

Instead of accounting for cycle length in era lengths, number of discreet era per cycle needs to be considered.

[github-actions]

Package	Line Rate	Branch Rate	Health
pallets/dapp-staking-v3/src/test	0%	0%	❌
pallets/static-price-provider/src	58%	0%	➖
chain-extensions/unified-accounts/src	0%	0%	❌
precompiles/xcm/src	72%	0%	➖
pallets/astar-xcm-benchmarks/src	89%	0%	✔
pallets/dapps-staking/src/pallet	86%	0%	✔
pallets/dapp-staking-migration/src	48%	0%	❌
chain-extensions/types/xvm/src	0%	0%	❌
precompiles/unified-accounts/src	100%	0%	✔
primitives/src	62%	0%	➖
chain-extensions/types/unified-accounts/src	0%	0%	❌
pallets/dapp-staking-v3/rpc/runtime-api/src	0%	0%	❌
pallets/collator-selection/src	89%	0%	✔
pallets/dapp-staking-v3/src	88%	0%	✔
precompiles/xvm/src	74%	0%	➖
chain-extensions/xvm/src	0%	0%	❌
pallets/ethereum-checked/src	75%	0%	➖
precompiles/dapps-staking/src	94%	0%	✔
pallets/astar-xcm-benchmarks/src/fungible	100%	0%	✔
pallets/block-rewards-hybrid/src	91%	0%	✔
chain-extensions/pallet-assets/src	56%	0%	➖
pallets/astar-xcm-benchmarks/src/generic	100%	0%	✔
pallets/dapp-staking-v3/src/benchmarking	98%	0%	✔
precompiles/dapp-staking-v3/src	90%	0%	✔
precompiles/substrate-ecdsa/src	74%	0%	➖
pallets/dapps-staking/src	90%	0%	✔
primitives/src/xcm	66%	0%	➖
chain-extensions/types/assets/src	0%	0%	❌
precompiles/dapp-staking-v3/src/test	0%	0%	❌
pallets/inflation/src	80%	0%	✔
pallets/xc-asset-config/src	64%	0%	➖
pallets/unified-accounts/src	84%	0%	✔
precompiles/assets-erc20/src	81%	0%	✔
precompiles/dispatch-lockdrop/src	86%	0%	✔
precompiles/sr25519/src	64%	0%	➖
pallets/xvm/src	51%	0%	➖
pallets/dynamic-evm-base-fee/src	92%	0%	✔
Summary	79% (4425 / 5602)	0% (0 / 0)	➖

Minimum allowed line rate is 50%