generate: emit bump files for consumers of changed catalog entries

[kaisermann]

Hey again 👋

Follow-up to #148/#149. check detects catalog changes and flags their consumers, but generate can't write the bump file check asks for.

Repro: https://github.com/kaisermann/bumpy-catalog-generate-repro (one workspace consuming react via catalog:, one commit bumping the catalog entry)

$ yarn bumpy check
error 1 changed package(s) missing bump files:

  bumpy-catalog-generate-repro-foo

$ yarn bumpy generate
=> Scanning commits on this branch (vs main)...
  Found 1 commit(s)
  Skipping (no matching packages): Bump react catalog entry to ^18.3.1
info No package bumps detected from commits.

generate maps commit files to packages by directory containment, and catalog files live at the repo root, so the commit matches no packages. Renovate or any catalog upgrade tool bumping one entry means hand-writing a bump file that lists every consumer.

Could generate maybe reuse the catalog diff check already does?