6 files declare their use of TextValue in Search API 8

AddHierarchy.php in src/Plugin/search_api/processor/AddHierarchy.php

BackendTest.php in modules/search_api_db/tests/src/Kernel/BackendTest.php

FieldsProcessorPluginBaseTest.php in tests/src/Unit/Processor/FieldsProcessorPluginBaseTest.php

StemmerTest.php in tests/src/Unit/Processor/StemmerTest.php

TestFieldsProcessorPlugin.php in tests/src/Unit/Processor/TestFieldsProcessorPlugin.php

TextDataType.php in src/Plugin/search_api/data_type/TextDataType.php