Replaces uses of `euclid::default::Size2D<u64>` with
`euclid::default::Size2D<u32>` for the canvas/context/snapshot.
This PR includes changes to the following components:
- canvas
- pixels
- script
- script_bindings
- shared/canvas
- shared/snapshot
Testing: https://github.com/hashcatHitman/servo/actions/runs/15426115391
(as of 892edc0048)
Fixes: #36706
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Signed-off-by: hashcatHitman <155700084+hashcatHitman@users.noreply.github.com>