feat(metering): use pending flashblocks state for bundle metering

[niran]

Summary

Enable bundle metering to use the current pending flashblocks state instead of just the canonical block state. This ensures that bundle simulations see the same state that will be used when the bundle is actually included in a flashblock.

Changes

Metering Crate

• meter.rs: Add PendingState struct containing BundleState and optional PendingTrieInput. Update meter_bundle to accept an optional PendingState parameter. Use with_bundle_prestate() to layer pending flashblock state on top of canonical state.
• rpc.rs: Update MeteringApiImpl to integrate with flashblocks API. Get pending blocks state and pass it to meter_bundle. Include state_flashblock_index in response.
• extension.rs: Update MeteringExtension to accept FlashblocksConfig for state access.
• lib.rs: Export PendingState and PendingTrieInput.

Flashblocks Crate

• state.rs: Add Default impl for FlashblocksState.
• extension.rs: Add Clone derive to FlashblocksConfig.
• tests/state.rs: Add integration tests verifying that bundle metering correctly sees pending flashblock state changes.

Architecture

Bundle Metering with Pending State:

┌─────────────────────────────────┐
│  State (bundle tracking)        │  ← Tracks bundle writes
│  with_bundle_prestate()         │  ← Includes flashblock state as prestate
├─────────────────────────────────┤
│  StateProviderDatabase          │  ← Reads from canonical chain state
└─────────────────────────────────┘

Test Plan

• Bundle metering correctly fails for nonce=1 tx without flashblock state (canonical nonce is 0)
• Bundle metering succeeds for nonce=1 tx with flashblock state showing pending nonce=1
• State visibility tests pass
• cargo +nightly clippy passes
• cargo +nightly fmt passes

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 2/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[refcell]

This looks good to me pending @danyalprout

[danyalprout]

thank you! this looks great