Revert superscheme

[dabreegster]

There's a critical problem with the superscheme PR: edits to the per-scheme pipeline form aren't preserved across page refresh. For the workshop tomorrow, it's more important to start collecting that form than to try showing multiple schemes at the same time.

A few problems that looked like they were introduced in the merge/rebase:

• The top-level GJ object has both a subschemes and a pipeline field: https://github.com/acteng/atip/blob/d9c99cac39163a4b975d7adaee5c2eef525bc2c6/src/types.ts#L15. The intention of pipeline was to wrap all the new scheme-level data in one place. subschemes and the format there don't match the browse page -- it's a third thing. We need to agree on what the GJ representation is -- see https://github.com/acteng/atip/pull/379#issuecomment-1784928203
• The PipelineScheme type is duplicated https://github.com/acteng/atip/blob/d9c99cac39163a4b975d7adaee5c2eef525bc2c6/src/types.ts#L107 and https://github.com/acteng/atip/blob/d9c99cac39163a4b975d7adaee5c2eef525bc2c6/src/types.ts#L122 -- I'm not sure what downstream type-checking issues this could cause
• There's some code duplication I find very confusing. PipelineSchemeDetails.svelte and EntireScheme.svelte have lots of overlap, and the new backfillSuperscheme is repeating the original backfill

I think my biggest confusion is why this new feature is specialized for the pipeline schema. In my mind, this should be tackling #152 -- a way to edit multiple files/layers/schemes for the same authority boundary in the sketch tool at the same time. It has nothing particular to do with the attributes we're collecting in the pipeline schema. We should think through https://github.com/acteng/atip/pull/379#issuecomment-1784928203 and settle what the GJ data looks like, how the UI should look, and then the implementation can follow from that.

My vote for the GJ representation is to support only two types of files: a single scheme and a combined scheme. We have both today (the second in the browse tool), and we can adjust them to better include the new pipeline fields

[robinlovelace-ate]

Important fix ready for workshop by the looks.

[dabreegster]

I'll merge to simplify all the rebasing for the pipeline branch. I'm also going to take a step back in the workshop tomorrow and ask:

• If it's clear when one scheme has many routes, vs when there are many schemes in the same area
• What the desired workflow will be for people filling out data in those areas with many schemes
• If they even want to edit multiple schemes at once, or if that'll be too confusing
• About the UI they'd expect