fix: omit bigint priceBumpPercentage from IPC config in testbench worker

[AztecBot]

Forward-port of #21086 to next.

childProcess.send() uses JSON serialization which cannot handle BigInt values. The priceBumpPercentage config field (added on v4 via backport) is a bigint that causes TypeError: Do not know how to serialize a BigInt when sent via IPC to worker processes.

This omits priceBumpPercentage from the IPC config via destructuring. On next the field doesn't exist in P2PConfig yet, so this is a preemptive fix that will prevent the issue when the field is merged forward. Uses Record<string, unknown> cast to avoid type errors on the destructure since the property doesn't exist in the current type.

ClaudeBox log: http://ci.aztec-labs.com/6d6b6eba6d0eecf1-5