Refactor BlockForType and BlockListBlock components

[geriux]

The BlockForType and BlockListBlock components need to be refactored for better performance and maintainability. The following changes should be made:

• Simplify the way styles are passed down to BlockForType by revisiting how we use getMergedGlobalStyles.
• Probably avoid using BlockForType I think this was added to be able to use hooks within BlockListBlock, maybe it's worth revisiting just removing it and integrating it with the main component.
• Reduce the length of the render method in BlockListBlock to improve performance.
• Refactor away from using class components for better readability and maintainability.
• Consider extracting the onMerge logic into a shared file, and check with the web team for their feedback.