Always split into multiple reports

[MattWellie]

This is definitely one for exploring...

The reports are massive, and without building an application to host/serve, we're stuck with a range of changes that are band-aids, instead of being proper fixes, e.g. splitting.

One that will buy us more time is a really hardcore scaling fix - splitting out the relevant parts of the report into different documents, each remaining a thin, standalone HTML document.

This change proposes snapping off the Variant Table overview (light) from the child rows (heavy), with hyperlinks in-between. This new approach would create a main page with a title, legend, and each variant. There would be links to the metadata (cohort size, distribution, panels, blacklist etc.)

The families in the table would link to a separate per-family document, containing the same main row/child row format as the current main page.

Hopefully this collection of pages will play ball with our GCP rendering of HTML using relative hyperlinks. We'll need relative links to make this work outside CPG