Investigate default attributes not saving for blocks.

[nerrad]

While working on and testing #2787, I noticed that default attributes are not saving for SSR grid blocks (All Products default attributes are saving) as expected from work done in #1613. Defaults are being used on initially added a block to content however.

I confirmed this was happening in master before merging #2787.

I don't know if this is a regression or if it is known based on changes between when #1613 was done and now (I may have missed something) but just creating this issue for tracking and potentially addressing if needed.

@mikejolley I'm just assigning to you for initial review since the two of us worked on #1613 initially. What are your thoughts?

[mikejolley]

@nerrad completely expected - the defaults and filter was added to the all products block only (seen here https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/1613/files#diff-500e1ea4e3573fafb7e29b070d9641e8R40). SSR blocks did not receive this treatment, so as per how gutenberg works, defaults are never saved to the block attributes.

I don't think it's worth rolling this change out for SSR and requiring more deprecation handling if we're moving away from SSR to Product Elements in the near future.

[nerrad]

Ahh makes sense, I wondered if it was something like that.