Remove some dd metrics

[zhouzhuojie]

FlagSnapshotID and SegmentID can be pushed for offline analytics. Not super useful in real-time monitoring for now.

[codecov-io]

Codecov Report

Merging #179 into master will increase coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
+ Coverage    90.7%   90.83%   +0.12%     
==========================================
  Files          25       25              
  Lines        1410     1408       -2     
==========================================
  Hits         1279     1279              
+ Misses         98       96       -2     
  Partials       33       33

Impacted Files	Coverage Δ
pkg/handler/eval.go	84.37% <ø> (+1.04%)	⬆️

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