allow order/sort for multiple select options

**Is your feature request related to a problem? Please describe.**
When I have a multiple select, the options that you select show in the order they were selected, not in the order that they are listed in options.

**Describe the solution you'd like**
I would love for selecting an option to put it into the displayed options/resulting saved value in the order that they show up in the original options specification. And/or optionally allow a sort key to specify what order the options should go into the resulting array.

**Describe alternatives you've considered**
I could use the boolean widget and list options so an order that makes sense is always presented, but this doesn't work with many values.

**Additional context**
My select options are time ranges (7am-8am, 8am-9pm, etc), so it gets confusing when they show up out of order. It also makes the code that uses it more complex, because it has to sort the values first before using them.

Here's an example:



The issue names no files or tests; start by locating the multiple-select widget and the code that builds its displayed and saved values. Compare the current selection-order behavior with the declared option order, then determine how an optional sort key should interact with both. Done means selected values can follow option order and the requested sorting behavior is covered.

Written by the indexing model from the issue text.