Change directives suffix to double hyphen instead of dot

[SantosGuillamot]

What?

I updated the current blocks to match the changes made in the Block Interactivity Experiments repo.

Why?

In the Block Interactivity Experiments repo, these changes were made because:

1. JSX doesn't support attributes with dots in them.
2. The term island has no meaning in WordPress, and we don't intend to embrace it.

How?

• Change the directives to use data-wp-on-- instead of the dot.