Implement base_meterPriorityFeePerGas so transactions can outbid resource constraints

[niran]

Adds metered priority fee estimation to the Base node, enabling bundles to receive priority fee recommendations based on real-time resource consumption from recent flashblocks.

base_meteredPriorityFeePerGas - Simulates a bundle and returns a recommended priority fee based on recent flashblock congestion across four resource dimensions:

• Gas - L2 gas consumption
• Execution time - CPU time spent executing transactions
• State root time - Time spent computing state roots
• Data availability - L1 DA bytes (dynamically updated via miner_setMaxDASize)

The estimator uses a displacement algorithm: for each resource, it finds the minimum priority fee required to displace enough existing transactions to make room for the bundle's resource demand, then takes the maximum across all resources and median across recent blocks.

Architecture

The metering pipeline consists of:

1. Kafka Consumer (KafkaBundleConsumer) - Consumes AcceptedBundle events from TIPS, extracting per-transaction resource usage
2. Resource Annotator - Correlates Kafka metering data with flashblock inclusions from the websocket feed, storing transactions in sequencer order
3. Metering Cache - Maintains recent block/flashblock metrics with automatic eviction and reorg detection
4. Priority Fee Estimator - Computes displacement-based fee estimates across multiple resource dimensions

CLI Configuration

--enable-metering                      Enable metering RPC
--metering-kafka-properties-file       Path to Kafka properties file
--metering-kafka-topic                 Topic name (default: tips-ingress)
--metering-kafka-group-id              Consumer group ID override
--metering-gas-limit                   Gas limit per flashblock (default: 30M)
--metering-execution-time-us           Execution time budget (default: 50ms)
--metering-state-root-time-us          State root time budget (optional)
--metering-da-bytes                    DA bytes limit (default: 120KB)
--metering-priority-fee-percentile     Percentile for fee recommendation (default: 0.5)
--metering-uncongested-priority-fee    Default fee when uncongested (default: 1 wei)
--metering-cache-size                  Blocks to retain (default: 12)

The metering system supports miner_setMaxDASize to dynamically update the limit for DA bytes allowed in a block.

Test Plan

• Unit tests for cache operations (insert, eviction, reorg clearing)
• Unit tests for estimator logic (displacement algorithm, congestion detection)
• Integration tests for annotator reorg handling
• Existing RPC tests continue to pass
• cargo +nightly fmt and cargo +nightly clippy pass

[cb-heimdall]

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