Add previous resource request to `lastRetry`

# Summary

Add the previous run memory request to lastRetry

## Use Cases

I'd like to be able to better control the memory request on retries. Sometimes I don't need to increase it (when the pod is evicted from a spot instance for example). On other occasions (OOMKilled) I'd like to exponentially increase it. Knowing the previous resource request along with [https://github.com/argoproj/argo-workflows/pull/12722](https://github.com/argoproj/argo-workflows/pull/12722 ) should make this possible.

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**Message from the maintainers**:

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Start at the existing lastRetry entry point and compare the behavior described in pull request #12722. Trace how retry metadata and resource requests are represented; done means lastRetry exposes the previous run's memory request so callers can distinguish eviction retries from OOMKilled retries, with relevant coverage added.

Written by the indexing model from the issue text.