Remove egg and wininst support

PyPI does not accept these distribution types since August 2023 and
there are no modern build backends that produce these, thus they are
most likely not used anymore.

egg support has only very minimal test coverage and had a fairly
obvious although likely inconsequential bug in reporting the target
Python version. wininst support has no tests.

Author: dnicolodi

changelog/1195.removal.txt

@@ -0,0 +1,2 @@
+- Remove support for ``egg`` and ``wininst` distribution types. These are not
+  accepted by PyPI and not produced by any modern build-backeds.

docs/internal/twine.rst

@@ -15,4 +15,3 @@ twine package
    twine.settings
    twine.utils
    twine.wheel
-   twine.wininst

docs/internal/twine.wininst.rst

@@ -463,12 +463,14 @@ def test_malformed_from_file(monkeypatch):
     assert "Invalid distribution file" in err.value.args[0]
 
 
-def test_package_from_egg():
-    filename = "tests/fixtures/twine-3.3.0-py3.9.egg"
-    package_file.PackageFile.from_filename(filename, comment=None)
-
-
 def test_package_from_sdist():
     filename = "tests/fixtures/twine-1.5.0.tar.gz"
     p = package_file.PackageFile.from_filename(filename, comment=None)
     assert p.python_version == "source"
+
+
+def test_package_from_unrecognized_file_error():
+    filename = "twine/package.py"
+    with pytest.raises(exceptions.InvalidDistribution) as err:
+        package_file.PackageFile.from_filename(filename, comment=None)
+    assert "Unknown distribution format" in err.value.args[0]

tests/fixtures/twine-3.3.0-py3.9.egg

@@ -44,19 +44,14 @@
 
 from twine import exceptions
 from twine import wheel
-from twine import wininst
 
 DIST_TYPES = {
-    "bdist_wheel": wheel.Wheel,
-    "bdist_wininst": wininst.WinInst,
-    "bdist_egg": pkginfo.BDist,
+    "wheel": wheel.Wheel,
     "sdist": pkginfo.SDist,
 }
 
 DIST_EXTENSIONS = {
-    ".whl": "bdist_wheel",
-    ".exe": "bdist_wininst",
-    ".egg": "bdist_egg",
+    ".whl": "wheel",
     ".tar.bz2": "sdist",
     ".tar.gz": "sdist",
     ".zip": "sdist",
@@ -157,13 +152,8 @@ def from_filename(cls, filename: str, comment: Optional[str]) -> "PackageFile":
                 )
             raise exceptions.InvalidDistribution(msg)
 
-        if dtype == "bdist_egg":
-            (dist,) = importlib_metadata.Distribution.discover(path=[filename])
-            py_version = dist.metadata["Version"]
-        elif dtype == "bdist_wheel":
+        if dtype == "wheel":
             py_version = cast(wheel.Wheel, meta).py_version
-        elif dtype == "bdist_wininst":
-            py_version = cast(wininst.WinInst, meta).py_version
         elif dtype == "sdist":
             py_version = "source"
         else: