gh-156510: Fix urlretrieve() file URL path on Windows

[vinitsonawane45]

Bug

urllib.request.urlretrieve() can return an invalid local path when given a file:// URL without an explicit filename argument on Windows.

Root cause

The no-filename fast path normalized a URL-formatted path using os.path.normpath(). On Windows, this can produce an invalid filesystem path.

Fix

Use url2pathname(url, require_scheme=True, resolve_host=True) on the complete file:// URL so it is correctly converted to a local filesystem path.

Tests

Added a regression test for urlretrieve() with a file:// URL and no explicit filename.

Fixes gh-156510.

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