Support overriding task pod_template via with_overrides

[arbaobao]

Tracking issue

Related to #5683

Why are the changes needed?

If we can support pod_template in with_overrides, this would reduce a lot of toil since we can supply pod templates in a central location and override downstream tasks, similar to how we can do so for resources.

What changes were proposed in this pull request?

We can use with_override() to override podtemplate, just like resources.

How was this patch tested?

Excute a workflow and using with_override(pod_template=PodTemplate(xxx)) to override the default podtemplate

Setup process

I ran flyte on my local machine and tested my code with this workflow and task:

python

@task
def say_hello() -> str:
    return "Hello, World!"

@workflow
def hello_world_wf() -> str:
    res = say_hello().with_overrides(limits=Resources(cpu="2", mem="600Mi"),pod_template=PodTemplate(
        primary_container_name="primary-nelson",
        labels={"lKeyA": "lValA", "lKeyB": "lValB"},
        annotations={"aKeyA": "aValA", "aKeyB": "aValB"},
        pod_spec=V1PodSpec(
            containers=[
                V1Container(
                    name="primary-nelson",
                    image="arbaobao/flyte-test-images:pythonpath5",
                    env=[V1EnvVar(name="eKeyC", value="eValC"), V1EnvVar(name="eKeyD", value="eValD")],
                ),
                V1Container(
                    name="primary-nelson2",
                    image="arbaobao/flyte-test-images:pythonpath5",
                    env=[V1EnvVar(name="eKeyC", value="eValC"), V1EnvVar(name="eKeyD", value="eValD")],
                ),
            ],
        )
    ))
    return res

Screenshots

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• I updated the documentation accordingly.
• All new and existing tests passed.
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Related PRs

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[arbaobao]

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