refactor: Strict null checks for all files except tests (#16071)

lib/config/types.ts

lib/modules/manager/types.ts

lib/util/git/index.ts

lib/workers/global/config/parse/host-rules-from-env.ts

lib/workers/global/config/parse/index.ts

lib/workers/global/index.ts

lib/workers/global/initialize.ts

lib/workers/repository/error-config.ts

lib/workers/repository/errors-warnings.ts

lib/workers/repository/finalise/index.ts

lib/workers/repository/finalise/prune.ts

lib/workers/repository/index.ts

lib/workers/repository/init/apis.ts

lib/workers/repository/init/vulnerability.ts

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

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

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

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

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

lib/workers/repository/onboarding/pr/config-description.ts