Revert "tests: reorganize unit tests into subdirectories mirroring source modules" (#10437)

tests/unit/README.md

@@ -11,19 +11,19 @@ poetry run pytest ./tests/unit
 Run specific test file:
 
 ```bash
-poetry run pytest ./tests/unit/llm/test_llm_fncall_converter.py
+poetry run pytest ./tests/unit/test_llm_fncall_converter.py
 ```
 
 Run specific unit test
 
 ```bash
-poetry run pytest ./tests/unit/llm/test_llm_fncall_converter.py::test_convert_tool_call_to_string
+poetry run pytest ./tests/unit/test_llm_fncall_converter.py::test_convert_tool_call_to_string
 ```
 
 For a more verbose output, to above calls the `-v` flag can be used (even more verbose: `-vv` and `-vvv`):
 
 ```bash
-poetry run pytest -v ./tests/unit/llm/test_llm_fncall_converter.py
+poetry run pytest -v ./tests/unit/test_llm_fncall_converter.py
 ```
 
 More details see [pytest doc](https://docs.pytest.org/en/latest/contents.html)