[backend] Persist 'only show completed orders' checkbox across pagination requests

Fixes #4004
Add changelog entry for #4004
[api] Add tentative caching to the parts that make up an order
Add changelog for order caching speedups
Use a more sensible method to get log entry partial name
When removing defunct zone members use classify instead of capitalize when deleting zone members by zonable_type.

When creating a custom zone member type like zip_code for example using capitalize removes all models with zonable type != Spree::Zip_code instead of Spree::ZipCode

Fixes #4001
Inventory Tracking by Variant: fix resource controller model load issue

Fixes #4016
Add missing backordered translation that backend build is complaining about
Revert "Use a more sensible method to get log entry partial name"

This reverts commit 181ba8c0aa3b2bc3adcc42f294a1b930272c2a78.