Entering a string of usernames in a user picker field no longer recognizes those names

Issue Summary

This is reproducible on Data Center: YES

Steps to Reproduce

1. Use Jira version 8.22 (it used to work in 8.20, no longer works in 8.22)
2. Create a user picker field and apply it to Issue screens.  
3. Attempt to enter a string of usernames without individually selecting the names.  

Expected Results

Previously you could enter multiple users via copy/paste.  

Actual Results

Now you must select each user separately.  

How it used to work on 8.20.3:

You could enter a string of names, and as long as they were all correct, it would select all those users.

How it works now on 8.22:

Shows results for the first match even after the second match is incomplete

BUT once the second match is complete, it stops matching (both of these are users)

You can no longer enter a string of names and have to enter all users separately.   

The inability to copy users from field and paste elsewhere, especially when there are multiple users in the field, increases the likelihood of missing someone or misspelling their names, now that customers have to type them out individually.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available