feat: currentVersionAgeInDays, newVersionAgeInDays (#31818)

docs/usage/configuration-options.md

lib/config/types.ts

lib/modules/manager/types.ts

lib/util/date.spec.ts

lib/util/date.ts

lib/util/template/index.ts

lib/workers/repository/process/lookup/generate.ts

lib/workers/repository/process/lookup/index.spec.ts

lib/workers/repository/process/lookup/index.ts

lib/workers/repository/process/lookup/types.ts