[WIP] Remove getOctokitClient for GitHub Actions v8 compatibility

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original prompt

Remove all uses of getOctokitClient which cannot work with the v8 version of the actions/github-acript.

Instead you need to split JavaScript in 2 steps and to run the graphql agent assign/review code with the agent token. See assign-to-agent JavaScript.

Delete the entire getOctokitClient helper file when done with refactoring.

Impacted: create-issue

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