Refactor `default mission impact values` in `collect.md` into an includable

Child of #522 

- Refactor the `Default Mission Impact Values` tip from `docs/howto/bootstrap/collect.md` into an includable file in `docs/_includes`
- Replace the tip in `collect.md` with the included tip
- Include the tip to the decision point reference page `docs/reference/decision_points/mission_impact.md`
- Include the tip in the "gathering info" page for mission impact
