fix(backend): MemoryKVCacheのキャッシュGC処理においてキャッシュが期限切れにならないことがある問題を修正

[samunohito]

What

タイトルの通りです。

Why

fix #15500

Additional info (optional)

テストを追加し、対応前の状態で流すとfailになること、対応後の状態で流すとpassになることを確認しています

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 15.26%. Comparing base (d74b646) to head (9ab5e05).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop   #17512      +/-   ##
===========================================
- Coverage    24.92%   15.26%   -9.67%     
===========================================
  Files         1160      245     -915     
  Lines        39555    12315   -27240     
  Branches     11016     4188    -6828     
===========================================
- Hits          9861     1880    -7981     
+ Misses       23796     8165   -15631     
+ Partials      5898     2270    -3628     

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[github-actions]

このPRによるapi.jsonの差分
差分はありません。
Get diff files from Workflow Page

[github-actions]

Backend memory usage comparison

Before GC

Metric	base (MB)	head (MB)	Diff (MB)	Diff (%)
VmRSS	306.16 MB	301.50 MB	-4.65 MB	-1.51%
VmHWM	306.16 MB	301.50 MB	-4.65 MB	-1.51%
VmSize	23171.79 MB	23166.45 MB	-5.34 MB	-0.02%
VmData	1372.28 MB	1366.82 MB	-5.45 MB	-0.39%

After GC

Metric	base (MB)	head (MB)	Diff (MB)	Diff (%)
VmRSS	306.32 MB	302.17 MB	-4.15 MB	-1.35%
VmHWM	306.32 MB	302.17 MB	-4.15 MB	-1.35%
VmSize	23171.79 MB	23167.20 MB	-4.59 MB	-0.01%
VmData	1372.28 MB	1367.57 MB	-4.70 MB	-0.34%

After Request

Metric	base (MB)	head (MB)	Diff (MB)	Diff (%)
VmRSS	306.65 MB	302.55 MB	-4.09 MB	-1.33%
VmHWM	306.65 MB	302.55 MB	-4.09 MB	-1.33%
VmSize	23171.79 MB	23167.20 MB	-4.59 MB	-0.01%
VmData	1372.28 MB	1367.65 MB	-4.62 MB	-0.33%

See workflow logs for details