Auto merge of #25432 - warren-fisher:HTMLConstructor, r=jdm

Extract some of CGClassConstructHook to utils.rs

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Moving some of the functionality from the massive tripled quoted string in CGClassConstructHook in `components/script/dom/bindings/codegen/CodegenRust.py` to `components/script/dom/bindings/utils.rs`. Must be made unsafe because of UnwrapObjectDynamic and other functions. Added imports as necessary as well, as well as cleaning up using test-tidy.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #25395 (GitHub issue number if applicable)

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because the issue says so

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