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)

.github/workflows/checks.yml

@@ -35,6 +35,7 @@ jobs:
       SKIP_WASM_BUILD: 1
       CARGO_INCREMENTAL: 0
       CARGO_TARGET_DIR: /cache/target
+      WASM_BUILD_WORKSPACE_HINT: ${{ github.workspace }}
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v4.1.7