fix(rc-runtime): remove old pezpallet_staking and related pallets for RC 1_020_006

StakingAhClient (index 67) is now Active — old NPoS staking on RC is unused.

Removed pallets:
- Staking (pezpallet_staking, index 9)
- FastUnstake (pezpallet_fast_unstake, index 15)
- VoterBagsList (pezpallet_bags_list Instance1, index 100)

Changes:
- Added NoopFallback struct for ah_client::Config::Fallback
- Updated validator_manager to use StakingAhClient
- Added RemovePallet migrations for on-chain storage cleanup
- Removed StakingConfig from genesis presets
- Cleaned up unused imports and dependencies
- Updated upgrade scripts (ah_upgrade, rc_upgrade, people_upgrade, set_ah_client_active)

Cargo.lock

@@ -14903,14 +14903,12 @@ dependencies = [
  "pezpallet-authority-discovery",
  "pezpallet-authorship",
  "pezpallet-babe",
- "pezpallet-bags-list",
  "pezpallet-balances",
  "pezpallet-beefy",
  "pezpallet-beefy-mmr",
  "pezpallet-collective",
  "pezpallet-conviction-voting",
  "pezpallet-election-provider-support-benchmarking",
- "pezpallet-fast-unstake",
  "pezpallet-grandpa",
  "pezpallet-indices",
  "pezpallet-message-queue",
@@ -14930,7 +14928,6 @@ dependencies = [
  "pezpallet-scheduler",
  "pezpallet-session",
  "pezpallet-session-benchmarking",
- "pezpallet-staking",
  "pezpallet-staking-async-ah-client",
  "pezpallet-staking-async-rc-client",
  "pezpallet-staking-runtime-api",