Unify metrics: cleanup and add missing metrics

[adarsh0728]

The PR aims to have unified metrics for source, sink.
Currently we are exposing metrics for different source types like kafka, http as well in addition to forwarder metrics.
Cleanup of such metrics as well as addition of any missing metrics like sink write latency etc.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.66%. Comparing base (9c1d3ce) to head (16db48b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2207      +/-   ##
==========================================
- Coverage   63.93%   63.66%   -0.27%     
==========================================
  Files         334      334              
  Lines       40676    40666      -10     
==========================================
- Hits        26006    25891     -115     
- Misses      13609    13715     +106     
+ Partials     1061     1060       -1     

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