BUG: Expand encoding for C engine beyond utf-16

And by utf-16, we mean the string "utf-16"

Closes pandas-dev#24130

Author: gfyoung

pandas/tests/io/parser/conftest.py

@@ -107,6 +107,32 @@ def python_parser_only(request):
 ]
 
 
+@pytest.fixture(params=_utf_values)
+def utf_value(request):
+    """
+    Fixture for all possible integer values for a UTF encoding.
+    """
+    return request.param
+
+
+@pytest.fixture(params=_encoding_fmts)
+def encoding_fmt(request):
+    """
+    Fixture for all possible string formats of a UTF encoding.
+    """
+    return request.param
+
+
+_utf_values = [8, 16, 32]
+
+_encoding_seps = ["", "-", "_"]
+_encoding_prefixes = ["utf", "UTF"]
+
+_encoding_fmts = [
+    f"{prefix}{sep}" + "{0}" for sep in _encoding_seps for prefix in _encoding_prefixes
+]
+
+
 @pytest.fixture(params=_utf_values)
 def utf_value(request):
     """