kafka: Optimizing the output of consume cli

[YangKian]

PR Description

Main changes:

$ hstream-kafka-cli --port 9092 consume -g c15 -t test-t --earliest -v

CreateTimestamp: 1703818135548   Key:                      vvv
CreateTimestamp: 1703669800783   Key:                      pfg
CreateTimestamp: 1703673787567   Key:                      dddd
CreateTimestamp: 1703661884636   Key: k3                   ccc
CreateTimestamp: 1703818141791   Key:                      vvvv
CreateTimestamp: 1703661880207   Key: k2                   bbb
CreateTimestamp: 1703661870948   Key: k1                   aaa

---

Checklist

• I have run format.sh under script
• I have commented my code, particularly in hard-to-understand areas
• New and existing unit tests pass locally with my changes