feat(platform): Cache created comments (#14279)

lib/platform/comment.spec.ts

lib/platform/comment.ts

lib/util/cache/repository/types.ts

lib/workers/branch/handle-existing.ts

lib/workers/branch/index.ts

lib/workers/pr/automerge.ts

lib/workers/pr/index.ts

lib/workers/repository/finalise/prune.ts

lib/workers/repository/onboarding/branch/check.ts

tsconfig.strict.json