Update KEP-1731 to include the latest implementation changes

[xmudrii]

We had to make some implementation changes for KEP-1731 (publishing packages to the community infra) along the way but these changes didn't made their way to the KEP. We need to ensure that the KEP is up to date as it might be used as the implementation reference in the future.

/assign
/sig release
/area release-eng
/priority important-soon

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/lifecycle stale