Fix problem with item name dropdown selection

[coalest]

Resolves #4547

Description

This issue occurs when an ajax call to populate the item names in the dropdown options occurs while the dropdown has been opened. Selecting an option doesn't work because that option no longer exists, so nothing happens (so item selected in the field will be the first item from the list of new options).

To fix this I made two changes:

1. Added an event listener so that whenever a item name dropdown option is selected, if the id of that item matches in the list of new options, select that option. (Note: This is enough to fix the bug)
2. But during investigation I found that when adding a new item, two ajax calls are fired off (to /inventory.json) every time you click "Add Another Item". And an ajax call is made to fetch the inventory whenever the storage location changes. I'm assuming it's not needed to fetch the inventory so often. So I changed it to only fetch the inventory item names/quantities on storage location field change, then we store those dropdown options and reuse them whenever a new line item is added.

This will make adding new line items more responsive, and with less jank (from the reduced number of ajax calls) (ie. the item name changing from "XL Diapers" to "XL Diapers (1353)").

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested manually in Chrome on my local machine, using the reproduction steps provided here.

Testing has been tough. I see a similar issue to the one I'm having where the inputevent isn't being triggered by cuprite. In my case the select2:select event isn't being triggered for some reason.