Tag status in encoding time metrics

[masih]

Tag the encoding time measurements with success/failure.

Fixes inconsistent error check across defer statements measuring time.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.18%. Comparing base (146ffe4) to head (d71d453).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #873      +/-   ##
==========================================
+ Coverage   67.11%   67.18%   +0.07%     
==========================================
  Files          84       85       +1     
  Lines        9175     9174       -1     
==========================================
+ Hits         6158     6164       +6     
+ Misses       2469     2465       -4     
+ Partials      548      545       -3     

Files with missing lines	Coverage Δ
internal/encoding/encoding.go	80.95% <100.00%> (+10.83%)	⬆️
internal/encoding/metrics.go	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes