Restructure Blob, structured serialization
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FIX#24052 and also address the "cloning" half of FIX#23917
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Issue 21810/improve validation methods
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This is a start at addressing #21810. I'm putting these changes out early to get some feedback on the following items:
1. I added unit tests for the validation methods mentioned in #21810, because I couldn't tell whether any of the existing WPT tests covered them. Are these tests worthwhile? Are any of them unnecessary?
2. I changed the implementation for `is_valid_floating_point_number_string` so that it passed the tests. The previous version of the function wasn't restrictive enough (it allowed certain whitespace characters before the number string).
3. I changed the catch-all condition in `htmlinputelement.rs` to account for the remaining input types that don't have a value sanitization algorithm. This last change seems good to me since we won't be able to add a new input type without adding it to the case and checking the spec for an algorithm.
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- [x] These changes fix#21810
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