Default logger fails to log BigInt

[Nevon]

Describe the bug
When enabling debug logging to investigate an unrelated issue, we started seeing TypeErrors from the logger.

This appears to be because offsets are BigInts and JSON.stringify doesn't know how to serialize those:

> const val = { foo: 100n }
undefined
> JSON.stringify(val)
Uncaught TypeError: Do not know how to serialize a BigInt
    at JSON.stringify (<anonymous>)

To Reproduce

Enable debug logging and run consumer.commitOffsets without first having run consumer.run. The debug message contains offsets which are BigInts.

Expected behavior
The log should serialize the bigints to strings.

Observed behavior

TypeError: Do not know how to serialize a BigInt
    at JSON.stringify (<anonymous>)
    at /home/klarna/app/node_modules/kafkajs/src/loggers/console.js:5:24
    at Object.debug (/home/klarna/app/node_modules/kafkajs/src/loggers/index.js:16:3)
    at Runner.commitOffsets (/home/klarna/app/node_modules/kafkajs/src/consumer/runner.js:467:19)
    at Object.commitOffsets (/home/klarna/app/node_modules/kafkajs/src/consumer/index.js:369:19)
    at KafkaJsClient.commit (/home/klarna/app/pubsub/kafkajs/index.js:115:14)
    at /home/klarna/app/consumer/index.js:314:101
    at Runner.eachMessage (/home/klarna/app/pubsub/kafkajs/index.js:55:21)
    at Runner.processEachMessage (/home/klarna/app/node_modules/kafkajs/src/consumer/runner.js:151:20)
    at onBatch (/home/klarna/app/node_modules/kafkajs/src/consumer/runner.js:287:20)

Environment:

• OS: Amazon Linux 2
• KafkaJS version: 1.15.0
• NodeJS version 12-something, but can reproduce in 14 and 16 as well