Refactor box-sizing for consistency across elements

[gitesh9]

Description

This PR refactors the box-sizing implementation to provide consistent behavior across all elements. It sets box-sizing: inherit globally for all elements, ensuring that child elements inherit their parent's box-sizing value. Additionally, box-sizing: border-box is applied to the root element, ensuring consistency across the entire document by default.

Motivation & Context

This change addresses the issue described in issue #41213 . The current implementation leads to inconsistent layout behavior when different box-sizing models are used for parent and child elements. By making this adjustment, we ensure that all elements inherit the same box-sizing behavior, improving consistency and maintainability.

Type of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Refactoring (non-breaking change)
• [ ] Breaking change (fix or feature that would change existing functionality)

Checklist

• [x] I have read the contributing guidelines
• [x] My code follows the code style of the project (using npm run lint)
• [ ] My change introduces changes to the #documentation
• [ ] I have updated the documentation accordingly
• [ ] I have added tests to cover my changes
• [ ] All new and existing tests passed

Related issues

Closes #41213

[mdo]

Saving this to revisit in v6 if we want it.