fix(controller): wrap trial status errors

[Epochex]

Fixes #2628.

This tightens the trial controller error wrapping so callers can use errors.Is / errors.As on the underlying failures:

• use errors.New for sentinel trial-controller errors
• wrap metric timestamp parse failures with %w
• wrap deployed job success/failure condition unmarshal errors with %w
• add regression coverage for the parse and JSON unmarshal error chains

Tested:

• go test ./pkg/controller.v1beta1/trial/util
• KUBEBUILDER_ASSETS=C:\Users\lin\AppData\Local\kubebuilder-envtest\k8s\1.34.0-windows-amd64 go test ./pkg/controller.v1beta1/trial ./pkg/controller.v1beta1/trial/util

The second command reaches PASS for the controller package tests on this Windows machine, then the command exits 1 because envtest cannot signal the local kube-apiserver and etcd processes to stop (not supported by windows).

[github-actions]

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[google-oss-prow]

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