[Multi_K8s-Plugin] Pin Is* methods to exact Kubernetes API groups

[mohammedfirdouss]

What this PR does:
Tightens the API group checks in provider/manifest.go. The Is* methods previously used isBuiltinAPIGroup() which accepted any of ~20 builtin Kubernetes API groups, a Deployment-like CRD from a non-apps group would pass IsDeployment(). Each method is now pinned to its exact API group:

• IsDeployment, IsStatefulSet, IsDaemonSet, IsReplicaSet → group must be "apps"
• IsService, IsSecret, IsConfigMap, IsPod → group must be "" (core)
• IsWorkload → applies the per-Kind group rule above

isBuiltinAPIGroup and the builtinAPIGroups map are now unused and have been removed.

Why we need it:
The loose check could misidentify a custom resource with the same Kind string but a different API group as a known Kubernetes workload or service, causing incorrect variant label injection or cleanup behaviour.

Which issue(s) this PR fixes:

Fixes #6446

Does this PR introduce a user-facing change?:

• How are users affected by this change: No change for standard Kubernetes resources. Users with CRDs that share a Kind name with a builtin resource (e.g. a CRD named Deployment in a non-apps group) will no longer have that resource treated as a workload which is the correct behaviour.
• Is this breaking change: No
• How to migrate (if breaking change): N/A

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 35.76%. Comparing base (5df1ef3) to head (4c9dbd4).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6784      +/-   ##
==========================================
+ Coverage   29.33%   35.76%   +6.43%     
==========================================
  Files         598       96     -502     
  Lines       63902     8399   -55503     
==========================================
- Hits        18744     3004   -15740     
+ Misses      43711     5230   -38481     
+ Partials     1447      165    -1282     

Flag	Coverage Δ
.	?
.-pkg-app-pipedv1-plugin-analysis	32.43% <ø> (ø)
.-pkg-app-pipedv1-plugin-ecs	31.82% <ø> (ø)
.-pkg-app-pipedv1-plugin-kubernetes	?
.-pkg-app-pipedv1-plugin-kubernetes_multicluster	?
.-pkg-app-pipedv1-plugin-scriptrun	54.83% <ø> (ø)
.-pkg-app-pipedv1-plugin-terraform	37.95% <ø> (ø)
.-pkg-app-pipedv1-plugin-wait	?
.-pkg-app-pipedv1-plugin-waitapproval	52.71% <ø> (ø)
.-pkg-plugin-sdk	50.34% <ø> (ø)
.-tool-actions-gh-release	19.23% <ø> (ø)
.-tool-actions-plan-preview	25.51% <ø> (ø)
.-tool-codegen-protoc-gen-auth	0.00% <ø> (ø)

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