Overrides in Synced Patterns: allow enabling overrides in parent blocks

[liviopv]

What problem does this address?

For the Buttons Block (and eventually other blocks like List, Group, Column, Cover, Gallery), users might want to create patterns where all the nested blocks can be overridden, not just specific nested items. There should be a setting inside the parent block give users this option

What is your proposed solution?

• Add a "Allow overrides in all nested blocks" option for blocks that only accept one type of nested block like Buttons, List, and Gallery
• Add a "Allow overrides in nested blocks that support it" in blocks that can accept multiple types of blocks, like Group, Column and Cover.

[gziolo]

I see that @talldan created later a similar issue that targets the Group block:

• https://github.com/WordPress/gutenberg/issues/61225

It could make sense to combine these two issues. The other one received many comments, so that could be a factor on deciding which one go with after moving all the details from this one there. What do you think?