chore(nxdev): reorganize nx-plugin content

[AgentEnder]

Reorganizes some docs content to move it into extending-nx menu.

DependsOn: #9757

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• nx affected --target=e2e --base=2177aae6eba87a3b8a504133efb7b9d0fef2efc5 --head=27bb939042d32ef6d3d8354eaeed8fa1a7c7eff0 --exclude=e2e-detox,e2e-js,e2e-next,e2e-workspace-create,e2e-workspace-integrations,e2e-workspace-core,e2e-react,e2e-web,e2e-angular-extensions,e2e-angular-core,e2e-cli,e2e-nx-plugin,e2e-cypress,e2e-node,e2e-linter,e2e-jest,e2e-a...

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