feat: introduce pallet-parameters to Westend to parameterize inflation (#4938)

Fixes #4907

## Changes
- Add `pallet-parameters` to Westend runtime
- Add `relay_era_payout` function to Polkadot runtime common + deprecate
previous `era_payout` function
- Add unit tests for `relay_era_payout`, matching previous unit tests
for `era_payout`
- Remove `pallet_staking_reward_curve` in Westend runtime
- Add `dynamic_params` to replace constants used for
`pallet_staking_reward_curve`

Polkadot address: 5DybbVdLvVWd7MiA1YwkzLUNL1ThMDicozbuLc8v9pQEScPQ

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Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: kianenigma <kian@parity.io>
Co-authored-by: command-bot <>