feat: add helm chart for training-operator

[vicoooo26]

What this PR does / why we need it:

Add a Helm chart for deploying the training-operator on Kubernetes. The chart includes all necessary CRDs (TFJob, PyTorchJob, JAXJob, MPIJob, PaddleJob, XGBoostJob), RBAC resources, webhook configuration, and configurable values for production deployments.

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):

Checklist:

• Docs included if any changes are user facing

[github-actions]

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[cheyang]

Early feedback (still a draft). The templates are in good shape — the fail guard on replicas>1 without leader election, the probes, the security context, and values.schema.json (incl. the min/maxUnavailable mutual-exclusion) are all nice; helm lint is clean and helm template renders. A few things stood out, mostly from a first-run user’s perspective:

• The PR description says “cert-manager integration”, but the chart doesn’t use cert-manager (no Certificate/Issuer, no caBundle / inject annotation). It relies on the operator’s built-in self-signed cert written into an empty Secret and patching the webhook caBundle at runtime (hence the validatingwebhookconfigurations: update grant). Worth correcting the description.
• The README install commands reference the aliyun-incubator/training-operator repo, but there’s no helm repo add aliyun-incubator <url> step — the documented install won’t work as written.
• Minor: CRDs under crds/ aren’t upgraded by Helm; a note in the README about applying CRD updates manually would help.