perf: optimize loading of django admin program pages

[zawan-ila]

PROD-4274

Description

Program admin pages are taking a long time to load and sometimes may even time out. Looking at the traces, most of the time is being spent in rendering the html widgets.

This PR makes the following changes:-

1. Add in_year_value to autocomplete_fields so that all ProductValue objects are not rendered in the html
2. While calculating optgroups on SortedModelSelect2Multiple widgets, do not include unselected options. This prevents the unselected options from being rendered in the html. django_autocomplete_light also appears to be doing the same thing
3. Currently, the sorting of SortedModelSelect2Multiple widgets is broken. We fix it by deferring the loading of sortable_select.js

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After