More work

- Consolidated "in_stock" filter to single code location
- Improve 'limit_choices_to' for BuildItem and SalesOrderAllocation
- Various template improvements etc

InvenTree/templates/table_filters.html

@@ -21,6 +21,11 @@ function getAvailableTableFilters(tableKey) {
                 title: '{% trans "Include sublocations" %}',
                 description: '{% trans "Include stock in sublocations" %}',
             },
+            in_stock: {
+                type: 'bool',
+                title: '{% trans "In stock" %}',
+                description: '{% trans "Item is in stock" %}',
+            },
             active: {
                 type: 'bool',
                 title: '{% trans "Active parts" %}',