Fix SVG even-odd fill rule imports (#4332)

[NicTanghe]

• ## Summary

Fixes SVG imports ignoring fill-rule="evenodd".

• Preserves the parsed fill rule as a vector attribute.
• Applies it consistently in SVG and Vello rendering.
• Keeps existing branching-vector fill behavior unchanged.
• Migrates existing Fill nodes with NonZero as the default.
• Adds regression tests for importing, propagation, and rendering.

Testing

• cargo test -p vector-nodes -p rendering -p graphite-editor
• 144 tests passed; 1 existing test ignored.
• cargo fmt --all -- --check
• git diff --check

Closes #4332.

[gemini-code-assist]

Code Review

This pull request introduces support for explicit vector fill rules (NonZero and EvenOdd) across the application. This includes defining the FillRule enum, updating the fill node to accept a fill rule input, implementing SVG and canvas rendering support for even-odd fills, and adding document migration logic to upgrade legacy fill nodes. Feedback suggests optimizing the document migration logic to avoid redundant node replacements when upgrading legacy fill nodes.

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[gemini-code-assist]

By directly setting the default FillRule input and updating inputs_count to 8 at the end of the inputs_count == 4 migration block, we can avoid entering the subsequent inputs_count == 7 block. This prevents redundant calls to replace_implementation and replace_inputs for the same node during a single migration pass, improving performance and reducing overhead.

Suggested change

	inputs_count = 7;
	document
	.network_interface
	.set_input(&InputConnector::node(*node_id, 7), NodeInput::value(TaggedValue::FillRule(FillRule::NonZero), false), network_path);
	inputs_count = 8;

[NicTanghe]

This was done to prevent other tests from failing.

[cubic-dev-ai]

All reported issues were addressed

Confidence score: 5/5

• Safe to merge after the addressed issues were fixed.

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