Restructure and Revise US Federal Working on Tickets Workflow for Collaboration

Why is this change being made?

In an effort to include non-US Federal focused engineers I'm proposing we de-silo some of the technical discussion around cases when asking for assistance by moving the conversation outside of the private #support_us-federal-chat channel. This can help get better exposure to SME's and give others the chance to participate in US Federal cases, even if indirectly (ie. not US citizens with access). Since we're not communicating confidential information in the private channel we should be transparent by default.

Also removes some of the outdated sections around the (currently) unused #feed_zd_federal channel

Author Checklist

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• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
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