fix(kbagent): reap zombie processes

[leon-ape]

Summary

• backport fix(kbagent): reap zombie processes #10763 to release-1.1
• run kbagent under tini and ship tini-static in the tools image
• preserve the legacy custom-image init image/command pair for existing Pods while new or recreated Pods copy both binaries
• centralize the current and legacy kbagent Pod contracts for Component and InstanceSet consumers

Backport notes

The commits were cherry-picked in order from #10763. Release-only resolutions keep the release-1.1 Apps implementation and adapt the branch's older getPodUpdatePolicy test signature.

Closes #10762

Verification

• scripts/codex-go-test.sh ./cmd/kbagent ./pkg/kbagent -count=1
• scripts/codex-go-test.sh -overlay=<generated-mock-overlay> ./pkg/controller/component ./pkg/controller/instanceset -count=1
• scripts/codex-go-test.sh -overlay=<generated-mock-overlay> ./controllers/apps/component -count=1
• built docker/Dockerfile-tools
• verified /bin/kbagent and /bin/tini-static are executable in the built image; tini reports 0.19.0

[apecloud-bot]

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[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.30%. Comparing base (dbf783b) to head (6d910ef).

Files with missing lines	Patch %	Lines
pkg/controller/instanceset/in_place_update_util.go	79.54%	6 Missing and 3 partials ⚠️
pkg/controller/instanceset/instance_util.go	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release-1.1   #10772      +/-   ##
===============================================
+ Coverage        54.25%   54.30%   +0.04%     
===============================================
  Files              545      546       +1     
  Lines            61364    61431      +67     
===============================================
+ Hits             33293    33359      +66     
- Misses           24876    24878       +2     
+ Partials          3195     3194       -1     

Flag	Coverage Δ
unittests	54.30% <84.21%> (+0.04%)	⬆️

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