feat!: shrink payload of the startImport endpoint (#33630)

.changeset/two-emus-wash.md

.../importer-pending-avatars/server/PendingAvatarImporter.ts

.../app/importer-pending-files/server/PendingFileImporter.ts

apps/meteor/app/importer/server/classes/Importer.ts

apps/meteor/app/importer/server/methods/startImport.ts

apps/meteor/client/views/admin/import/PrepareImportPage.tsx

apps/meteor/lib/callbacks.ts

apps/meteor/server/services/import/service.ts

apps/meteor/tests/e2e/fixtures/files/csv_import.zip

apps/meteor/tests/e2e/fixtures/files/csv_import_users.csv

apps/meteor/tests/e2e/imports.spec.ts

apps/meteor/tests/e2e/page-objects/admin.ts

packages/core-typings/src/import/IImporterShortSelection.ts

packages/core-typings/src/import/index.ts

packages/rest-typings/src/v1/import/StartImportParamsPOST.ts