Encapsulation of tools/special_phrases.py into SpecialPhrasesImporter class and add new tests.

test/python/test_tools_exec_utils.py

@@ -9,13 +9,6 @@ import pytest
 
 import nominatim.tools.exec_utils as exec_utils
 
-@pytest.fixture
-def tmp_phplib_dir():
-    with tempfile.TemporaryDirectory() as phpdir:
-        (Path(phpdir) / 'admin').mkdir()
-
-        yield Path(phpdir)
-
 @pytest.fixture
 def nominatim_env(tmp_phplib_dir, def_config):
     class _NominatimEnv: