fix(anvil): use fee manager as Tempo fork coinbase

[BROCCOLO1D]

Summary

• Defaults Anvil Tempo forks to the Tempo fee manager address as block.coinbase/beneficiary when no genesis coinbase is supplied.
• Applies the same default when anvil_reset starts forking from a non-forked Tempo node.
• Keeps explicit genesis coinbase configuration unchanged.

Why

Tempo mainnet maps the zero-address validator token to a DONOTUSE sentinel. In fork mode, Anvil previously inherited the default zero beneficiary, so state-changing transactions could hit Tempo fee collection failures and then appear as missing receipts indefinitely. Tempo node-side simulation already uses the fee-manager sentinel to fall back to PathUSD.

Changes

• Centralized the Tempo fork beneficiary default in NodeConfig.
• Applied the default during Tempo fork startup and during anvil_reset when it initializes a fork from a non-forked node.
• Added regression coverage for both startup forks and reset-to-fork flows.

Validation

• git diff --check
• cargo fmt --check
• cargo test -p anvil --test it tempo::test_tempo

Scope

Small Anvil Tempo fork/default-beneficiary behavior only; does not alter non-Tempo forks, standalone Tempo nodes, or explicit genesis coinbase settings.

Refs #14866

[figtracer]

two findings.