feat(configmapset): enables zero-downtime configuration updates

[Placeboy]

Ⅰ. Describe what this PR does

This PR implements ConfigMapSet, a sidecar-based multi-version configuration manager that decouples configuration updates from image updates.
For instances of the same workload, while image versions are managed by CloneSet, configuration versions can be managed independently via ConfigMapSet.

This feature is enabled by injecting a sidecar container into each Pod. When the configuration version changes, the sidecar container restarts and rewrites the corresponding configuration version to the mounted path.

Ⅱ. Does this pull request fix one issue?

NONE

Ⅲ. Describe how to verify it

1. Create a ConfigMapSet (CMS) resource.
2. Deploy a workload whose label selector matches the CMS.
3. Adjust the version weights in the CMS to control the distribution of configuration versions.
4. Verify that:
   • The Pods restart as expected upon configuration version change.
   • Each Pod uses the correct version of the configuration as defined in CMS.

Ⅳ. Special notes for reviews

N/A

[kruise-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[kruise-bot]

Welcome @Placeboy! It looks like this is your first PR to openkruise/kruise 🎉

[codecov]

Codecov Report

❌ Patch coverage is 0.11293% with 1769 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.50%. Comparing base (6bc00ac) to head (14c9794).

Files with missing lines	Patch %	Lines
...controller/configmapset/configmapset_controller.go	0.17%	1136 Missing ⚠️
.../webhook/pod/mutating/pod_create_update_handler.go	0.00%	274 Missing ⚠️
...t/validating/configmapset_create_update_handler.go	0.00%	163 Missing ⚠️
pkg/controller/configmapset/configmapset_utils.go	0.00%	88 Missing ⚠️
...troller/configmapset/configmapset_event_handler.go	0.00%	74 Missing ⚠️
...set/mutating/configmapset_create_update_handler.go	0.00%	21 Missing ⚠️
pkg/webhook/configmapset/validating/webhooks.go	0.00%	6 Missing ⚠️
pkg/webhook/add_configmapset.go	0.00%	3 Missing ⚠️
pkg/webhook/configmapset/mutating/webhooks.go	0.00%	3 Missing ⚠️
pkg/controller/controllers.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2149      +/-   ##
==========================================
- Coverage   44.82%   42.50%   -2.33%     
==========================================
  Files         318      326       +8     
  Lines       32245    34016    +1771     
==========================================
+ Hits        14455    14457       +2     
- Misses      16370    18139    +1769     
  Partials     1420     1420              

Flag	Coverage Δ
unittests	42.50% <0.11%> (-2.33%)	⬇️

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[furykerry]

plz consider extract the RestartInjectedContainers field to a separate field in the ConfigMapSetSpec, maybe called "LoadStrategy", with three possible option

1. RestartAppContainers
2. RestartReloaderContainer
3. None

[furykerry]

consider move the pod mutating logic of comfigmapset into a sperate file e.g. configmapset.go

[furykerry]

how to config the image and possible container configuration such as poststarthook? Maybe we can add another CRD called ReloaderClass.