KubernetesPodOperator doc-string update templated fields + wording

[insomnes]

• Marking the new templated fields added in Expand KPO template_fields, fix Spark k8s operator tests #46268 in doc-string
• Marking some other missing templated fields in doc-string
• Update wording to use "container" instead of docker

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[insomnes]

As a side-node: I have a strong feeling that the image field is wrongly documented and typed, it's required by pod spec, and will not run with a None value, but I didn't test this hypothesis.

[potiuk]

As a side-node: I have a strong feeling that the image field is wrongly documented and typed, it's required by pod spec, and will not run with a None value, but I didn't test this hypothesis.

Not sure either. But I am not very worrried - (though if someone would like to check it that woudl be cool).