Resolve "Assign an integration epic to each component"

In short, this exposes the epic URL in rule definitions in the dashboard. It does not add epic links to rules; that can happen in other MRs.

In long:

• Show migration guide link in scan findings in drawer.
• Add example filters for rules with/without migration guides.
• Add a "Migration guide" option to group findings into "Yes" and "No".
• Add a note to treemap tooltips for findings without migration guides.
• Change the layout of treemap nodes for better readability.
• Indicate on treemap nodes if there isn't a migration for its findings. (This works because every node is always findings for a single rule.)
• Add migration guide column to rules table.
• When creating issues, add the issue to the epic, if it's defined.

Screenshots

Before	After

Review/run this locally

1. Copy the pages in mr job URL (must have succeeded)
2. Run bin/review-mr.sh <job url>

Closes #52