chore: drop toml, use tomli (#876)

This is required to get TOML 1.0 support, and lightens our dependencies a bit.

unit_test/build_ids_test.py

@@ -1,28 +1,32 @@
-import toml
+from typing import Dict, List
+
+import tomli
 from packaging.version import Version
 
-from cibuildwheel.extra import InlineArrayDictEncoder  # noqa: E402
+from cibuildwheel.extra import Printable, dump_python_configurations
 from cibuildwheel.util import resources_dir
 
 
 def test_compare_configs():
-    with open(resources_dir / "build-platforms.toml") as f:
-        txt = f.read()
+    with open(resources_dir / "build-platforms.toml") as f1:
+        txt = f1.read()
 
-    dict_txt = toml.loads(txt)
+    with open(resources_dir / "build-platforms.toml", "rb") as f2:
+        dict_txt = tomli.load(f2)
 
-    new_txt = toml.dumps(dict_txt, encoder=InlineArrayDictEncoder())  # type: ignore
+    new_txt = dump_python_configurations(dict_txt)
     print(new_txt)
 
     assert new_txt == txt
 
 
 def test_dump_with_Version():
-    example = {
+    # MyPy doesn't understand deeply nested dicts correctly
+    example: Dict[str, Dict[str, List[Dict[str, Printable]]]] = {
         "windows": {
             "python_configurations": [
                 {"identifier": "cp27-win32", "version": Version("2.7.18"), "arch": "32"},
-                {"identifier": "cp27-win_amd64", "version": Version("2.7.18"), "arch": "64"},
+                {"identifier": "cp27-win_amd64", "version": "2.7.18", "arch": "64"},
             ]
         }
     }
@@ -35,6 +39,6 @@ python_configurations = [
 ]
 """
 
-    output = toml.dumps(example, encoder=InlineArrayDictEncoder())  # type: ignore
+    output = dump_python_configurations(example)
     print(output)
     assert output == result