Auto select first Nav Menu in Nav block if only a single wp_navigation exists

[getdave]

Currently when switching to a new Theme the Nav block requires the user to select the Nav Menu they wish to use in the Nav block. This is because there is no mechanism to decide on the most "appropriate" Nav Menu to use.

In order to optimise for the 80% use case where the user has a single Navigation Menu, let's update the block to automatically use the first Navigation Menu if there is only a single wp_navigation post.

cc @mtias @scruffian

[mtias]

To contextualize a bit more this idea, the general aim is to make the navigation renderer just work with the user's stored menu. The assumption being that if there is a single menu on a site we should try to use it.

[github-actions]

Hi,
This issue has gone 180 days without any activity. This means it is time for a check-in to make sure it is still relevant. If you are still experiencing this issue with the latest versions, you can help the project by responding to confirm the problem and by providing any updated reproduction steps.
Thanks for helping out.

[getdave]

This Issue has been completed by #42735 and others. Closing as complete.