Merged 8.8.11.

core/includes/file.inc

core/modules/file/file.module

...ules/file/src/Plugin/rest/resource/FileUploadResource.php

core/modules/file/tests/file_test/src/Form/FileTestForm.php

...e/tests/file_test/src/Form/FileTestSaveUploadFromForm.php

.../modules/file/tests/src/Functional/SaveUploadFormTest.php

core/modules/file/tests/src/Functional/SaveUploadTest.php

core/modules/file/tests/src/Kernel/ValidateTest.php

...napi/src/Controller/TemporaryJsonapiFileFieldUploader.php

core/modules/jsonapi/tests/src/Functional/FileUploadTest.php

.../rest/tests/src/Functional/FileUploadResourceTestBase.php

core/tests/Drupal/KernelTests/Core/File/NameMungingTest.php