feat: Support rcAt for /pallets/* endpoints

[TarikGul]

Summary

• Adds rcAt parameter support to multiple pallets endpoints for Asset Hub relay chain integration
• Enhances responses with relay chain context when rcAt parameter is used

Endpoints with rcAt support added:

• /pallets/nomination-pools/info
• /pallets/nomination-pools/{poolId}
• /pallets/on-going-referenda
• /pallets/{palletId}/consts
• /pallets/{palletId}/consts/{constItemId}
• /pallets/{palletId}/dispatchables
• /pallets/{palletId}/dispatchables/{dispatchableItemId}
• /pallets/{palletId}/errors
• /pallets/{palletId}/errors/{errorItemId}
• /pallets/{palletId}/events
• /pallets/{palletId}/events/{eventItemId}
• /pallets/{palletId}/storage
• /pallets/{palletId}/storage/{storageItemId}
• /pallets/pool-assets/{assetId}/asset-info
• /pallets/staking/validators

[filvecchiato]

Nice! Looking good!