Use pen widths when drawing ImageDraw2 shape outlines

[xiehuanyi]

Fixes #10206.

ImageDraw2.Pen(width=4) draws a four-pixel line, but shape outlines still have width one. Forward the selected pen width for arc, chord, ellipse, pieslice, polygon and rectangle, while preserving explicit render(width=...) overrides. Document the width and add a release note.

Regression tests compare all seven drawing operations with ImageDraw, with the pen in either argument position, and check rectangle border pixels directly. Existing shared-fixture tests now request width one, matching their fixture; the new tests cover wider outlines.

Validation on a fresh build of main with Python 3.12.13: 13 regressions fail before the fix, with 16 controls passing. After the fix, ImageDraw2/ImageDraw suites pass (341 tests, one existing expected failure), source selftest passes (59 tests), and ImageDraw2 coverage exercises the changed line. Configured mypy passes across all 303 source files. All applicable project pre-commit hooks pass, including pinned Black 26.10.0, Ruff 0.16.10, Bandit and Sphinx lint; Black 26.3.1 and diff checks pass too.

Discovered through a code audit, with the reproducer, patch and tests prepared and verified using GPT-6.1 Sol.

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[radarhere]

It appears that when #3094 added width support to the ImageDraw shapes, no one ever fully thought through how it applied to ImageDraw2.

I've remove the release note, as this is an obscure function as far as Pillow use goes.