fix: revise kafka sink conf/metrics

[Yisaer]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 63.88889% with 13 lines in your changes missing coverage. Please review.

Project coverage is 71.11%. Comparing base (0c6f4a0) to head (a003336).

Files with missing lines	Patch %	Lines
extensions/impl/kafka/sink.go	68.18%	7 Missing ⚠️
metrics/metrics.go	0.00%	5 Missing ⚠️
extensions/impl/kafka/source.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3494      +/-   ##
==========================================
+ Coverage   71.07%   71.11%   +0.04%     
==========================================
  Files         416      418       +2     
  Lines       48001    48016      +15     
==========================================
+ Hits        34112    34143      +31     
+ Misses      11219    11208      -11     
+ Partials     2670     2665       -5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.