Accurate sizes: Disable layout calculations for classic themes

[mukeshpanchal27]

Summary

This PR Checks the functionality of the image block in classic themes. After merging #1738, the sizes attribute for the classic theme has been producing incorrect values.

Issue Example:
When selecting the wide alignment for an image block, the sizes attribute is rendered as: sizes="(max-width: ) 100vw, ", This is incorrect. The expected output should be: sizes="(max-width: 1024px) 100vw, 1024px"

This PR aims to fix this issue and ensure the sizes attribute is generated correctly for classic themes.

Steps to reproduce the issue

• Activate classic theme (TT1)
• Add image block and select wide alignment
• Check frontend.

[github-actions]

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Co-authored-by: mukeshpanchal27 <[email protected]>
Co-authored-by: joemcgill <[email protected]>

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[joemcgill]

That makes sense because classic themes won't have a layout setting for this value. We could consider making a default guess, but disabling for now is probably sensable.

[felixarntz]

@mukeshpanchal27 @joemcgill This PR looks good to me, though a related question: Do we already have an issue to explore adding a way to define those widths for classic themes?

[joemcgill]

@felixarntz creating an API for defining layout values in classic themes is listed in the todo list for #760, but we've not yet created an issue for this yet. I wanted us to explore the implementation in the block theme context first before starting to define what that API should look like.