fix: fix storage v2 cgo mem leak

[shaoting-huang]

related: #39173

[mergify]

@shaoting-huang E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.53%. Comparing base (de02a3e) to head (7aa8ea2).
Report is 9 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #40305       +/-   ##
===========================================
+ Coverage   69.88%   80.53%   +10.65%     
===========================================
  Files         309     1470     +1161     
  Lines       27705   206760   +179055     
===========================================
+ Hits        19362   166519   +147157     
- Misses       8343    34197    +25854     
- Partials        0     6044     +6044     

Components	Coverage Δ
Client	79.16% <ø> (∅)
Core	69.88% <ø> (ø)
Go	82.33% <100.00%> (∅)

Files with missing lines	Coverage Δ
internal/storagev2/packed/packed_reader.go	75.51% <100.00%> (ø)
internal/storagev2/packed/packed_writer.go	79.31% <100.00%> (ø)

... and 1159 files with indirect coverage changes

[shaoting-huang]

/run-cpu-e2e

[mergify]

@shaoting-huang E2e jenkins job failed, comment /run-cpu-e2e can trigger the job again.

[shaoting-huang]

/run-cpu-e2e

[tedxu]

/lgtm
/approve

[sre-ci-robot]

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