Add target blank to server rendering of blocks.

[thijsoo]

Context

• We want to make sure that our links work in the new Iframe editor.

Summary

This PR can be summarized in the following changelog entry:

• improves the compatibility with WordPress 6.7 Iframe editor.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Install Yoast SEO and WP beta
• Activate WP 6.7-betaX
• Create a post and Breadcrumbs block there
• Click on Home in breadcrumbs
• Make sure you open your link in a new tab.
• Save the page en make sure the target blank is not active on the front-end.

Relevant test scenarios

• [ ] Changes should be tested with the browser console open
• [ ] Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• [ ] Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• [ ] Changes should be tested on different browsers
• [ ] Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• [X] QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• [ ] This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• [ ] This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• [ ] I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• [X] I have tested this code to the best of my abilities.
• [ ] During testing, I had activated all plugins that Yoast SEO provides integrations for.
• [ ] I have added unit tests to verify the code works as intended.
• [ ] If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• [ ] I have written this PR in accordance with my team's definition of done.
• [ ] I have checked that the base branch is correctly set.

Innovation

• [X] No innovation project is applicable for this PR.
• [ ] This PR falls under an innovation project. I have attached the innovation label.
• [ ] I have added my hours to the WBSO document.

Fixes #