Update Engineering offsite with more details

Why is this change being made?

Three changes, mostly unrelated to each other:

1. Add a link to the agenda for the FY23 Q1 offsite.
2. Move succession planning to every six months (every two offsites), per @rtakken.
3. Suggest, but don't require, GitLab epics to track actions from the FY direction for each department.

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added.
• Assign reviewers for this change to the correct DRI(s)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the "Maintained by" section in on the page being edited.
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies.

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