#15057 Summary

This PR can be summarized in the following changelog entry:

• Fixes an issue where breadcrumbs were being saved in reversed order.

Relevant technical choices:

• The indexable hierarchy table is truncated in a migration. This table is only ever used as a cache and thus no reindex is required. For sites with very long breadcrumbs and/or a lot of terms the first request to each post may be slightly slower ( generating the breadcrumbs would be about the same speed as it was in 13.5 ).

Test instructions

This PR can be tested by following these steps:

• Make sure you have breadcrumbs at least 5 layers deep: home -> grandparent term -> parent term -> child term -> post.
• Save that post with the child term as the primary category. Check the breadcrumb.
• Save that post with the parent term as the primary category. Check the breadcrumb.
• Do the same with a custom post type and custom taxonomy.
• Do the same with nested pages ( home -> grandparent page -> parent page -> child page ).
• In all cases the breadcrumb shown in both schema and by adding the breadcrumb to your theme as described here should show the correct order.

UI changes

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

Documentation

• I have written documentation for this change.

Quality assurance

• I have tested this code to the best of my abilities
• I have added unittests to verify the code works as intended

Fixes #15173
---- For acceptance testing -----
Probably fixes #15261 and #15251. Close these issues if fix confirmed in 14.2 RC