Renovate to nixica/horizon-advance shape (9.8.x)

Restructures lts/ghc-9.8.x to the canonical nixica + import-tree shape, refreshes horizon-advance lock to current head (picks up !207 (closed) + !210 (closed)), and adds 4 platform-specific transitive overrides (lucid, relude, mtl-compat, modern-uri). See commit message for full details.